The name Macmillan may also be spelled McMillan or Mac Millan for the same individual. The name Mclarty has many spellings. I am accepting the customary family spellings of Macmillan and Mclarty. Kilbride, Kilmory and Lochranza are on the Isle of Arran, in the Firth of Clyde, county of North Ayrshire (formerly Bute), Scotland. Any date for "birth" listed before 1855 in Scotland is a date of baptism, not birth.

Margaret Mclarty "Maggie" Macmillan 1894 is a daughter of Alexander "Alister" Macmillan (Alexander McMillan, son of Neil McMillan and Margaret Mclarty, born 27 January 1870 Kilbride, Bute, Scotland; Alister Macmillan was the hotel keeper of Lochranza Hotel, Isle of Arran, Scotland; Alister Macmillan died (born 1870, age 37) in 1907 in district of Lochranza (556/00 0008), county of Bute, Scotland); Alexander Macmillan, age 24, bachelor, hotel keeper of the Lochranza Hotel, Isle of Arran, son of Neil Macmillan and Margaret Maclarty, married his "cousin-once-removed" (second-cousin), Mary Maclarty, age 33, spinster, daughter of Ronald Maclarty and Christian "Christina" McAllister, on 02 February 1894 at The Bath Hotel, Bath Street, Glasgow, after banns according to the forms of the Free Church of Scotland; Mary Mclarty (daughter of Ronald Mclarty and Christian "Christina" McAllister, born (11 AM) on 14 February 1857 in district of Kilmory (554/00 0009), county of Bute, Scotland; Mary Mclarty Macmillan died, no known date or place of death but sometime after 1915).
Alexander "Alister" and Mary had: 1 Margaret Mclarty Macmillan (1894-1974), 2 Alister Ian "Ian" Macmillan (born in 1896 in district of Lochranza (556/00 005), county of Bute, Scotland; in 1926, Ian (Alister) Macmillan lived at 16 Tunnel St., Riddrie, Glasgow; source: brother, Ronald Neil Macmillan, 1926 ship's log s/s Cedric; Ian Alister Macmillan, born 1896, died in 1985 in Bute, Scotland), and 3 Ronald Neil Macmillan (registered: Ranald Neil Macmillan born 1901 in district of Lochranza (556/00 0003), county Bute, Scotland; Ronald Neil Macmillan married in 1931 in Scotland; possible death: Ronald N. Macmillan died (age 49) 1st quarter 1951 in district of Kensington (Volume 5c, Page 1645), county of London, England).

In the following: Christian McAllister Mclarty, wife of Ronald Mclarty and mother of Mary Mclarty Macmillan, is baptised and married with the name of Christian, but also uses Christina.

Mary Mclarty 1857 is a daughter of Ronald "Ross" McLarty (Ronald MacLaharty, son of Ronald MacLaharty and Isabel Currie, baptised on 19 July 1812 Kilmory, Bute, Scotland; Ronald was a joiner; Ronald Mclarty of Arran, Scotland, went missing on the NY Great Lakes in May 1869; source: NY Herald, 15 May 1869: Information Wanted-of Wm. McKinnon, Gavin Hamilton and Ronald McLarty, of Arran, Scotland, supposed to be sailing on the lakes. Any person having seen them, please communicate to John McKinnon, 10 Renwick Street, NY; Ronald Mclarty, son of Ronald McLarty, farmer, deceased, and Isabella McLarty nee Currie, died (age 62, of cancer of the liver) on 13 August 1874 in district of Kilmory (554/00 0028), at Balmichael, Kilmory parish, county of Bute, Scotland; Ronald Mclarty married Christian McAlister on 14 March 1844 in parish of Kilmory, Shiskine and Lochranza (554/00 0030 0178), county of Bute, Scotland; Christian "Christina" McAllister (Christian McAllister, female, daughter of Matthew McAllister and Janet McKennon (McKinnon), baptised on 28 July 1816 in parish of Kilmory, Shiskine and Lochranza (554/00 0020 0069), county of Bute, Scotland; Christian is also listed as Christina in some Scotland censuses; in 1881 Scotland Census, Christina Mclarty (McLarby), born c. 1818 Kilmory, Bute, lived with her married daughter, Jane Mclarty Thomson (m. Henry D. 1877) in Dalmellington, Ayrshire; possible death: Christina Mclarty died in 1899 in county of Bute, Scotland.
Ronald "Ross" and Christian "Christina" had: 1 Isabella Mclarty 1847, 2 Janet Mclarty 1849, 3 Margaret Mclarty 1850, 4 Jane Mclarty Thomson (1854, wife of Henry D. Thomson), 5 Mary Mclarty Macmillan (1857-after 1915, wife of Alexander "Alister" Macmillan and mother of Margaret Mclarty Macmillan Mitchell Macmillan), and 6 John Mclarty 1860.

Ronald McLarty 1812 is a son of Ronald Maclarty married Isabel Curry (Currie) on 23 December 1794 in parish of Kilmory, Shiskine and Lochranza (554/00 0010 0203), county of Bute, Scotland; unable to identify birth/baptism or death for Ronald McLarty or Isabel Curry (or Currie) McLarty.
Ronald and Isabel had (all children baptised in Kilmory, Bute, Scotland; all children listed with parents: Ronald Mclarty (or name variant) and Isabel Currie (or name variant Curry); the first two children are baptised on the same day in 1796, they may or may not be twins): 1 Donald Mclarty (Maclaerty) baptised on 18 August 1796, 2 Margaret Mclarty (Maclaerty) baptised on 18 August 1796, 3 John Mclarty (John Maclaharty baptised on 14 June 1798-1868, husband of Jean McMurray and father of Margaret Mclarty Macmillan), 4 Archibald Mclarty (MacLaerty) baptised on 05 June 1800, Alexander Mclarty (MacLaerty) baptised on 25 November 1804, 5 James Mclarty (MacLaerty) baptised on 04 July 1802, 6 Mary Mclarty (MacLaerty) baptised on 08 February 1807, 7 Elspa Mclarty (Maclaharty) baptised on 04 August 1809, 8 Ronald Mclarty (Ronald Maclaharty baptised on 19 July 1812-1874, husband of Christian "Christina" McAllister and father of Mary Mclarty Macmillan), and 9 Lauchlan Mclarty (Maclaharty) baptised on 19 November 1815; in 1841 Scotland Census, Lauchlan Mclarty was listed with Angus McMillan in Kilmory; no further data.

Alexander "Alister" Macmillan 1870 is a son of Neil MacMillan (son of Alexander MacMillan and Catharine Kelso, baptised on 29 August 1817 in parish of Kilmory, Shiskine and Lochranza (554/00 0020 0161), county of Bute, Scotland; Neil McMillan died (age 75) in 1891 in district of Lochranza (556/00 0003), county of Bute, Scotland; Neil Mcmillan, age 50, son of Alexander McMillan, farmer, deceased, and Catherine Mcmillan nee Kelso, deceased, married Margaret Fullerton Mclarty, age 27, daughter of John Mclarty, innkeeper, and Jean Mclarty nee McMurray, deceased, on 23 December 1867 in district of Lochranza (556/00 0006), Lochranza, Bute, Scotland, after Banns according to the forms of the Free Church of Scotland; Margaret Maclarty (daughter of John Mclarty and Jean McMurray, baptised on 24 June 1840 in parish of Kilmory, Shiskine and Lochranza (554/00 0030 0203), county of Bute, Scotland; Margaret Mclarty McMillan died (age 35) in 1876 in district of Lochranza (556/00 0008), county of Bute, Scotland.
Neil and Margaret Fullerton had: 1 Alexander "Alister" McMillan (Alexander McMillan, son of Neil and Margaret Mclarty McMillan, born 27 January 1870 Lochranza, Bute, Scotland; Alister Macmillan was a hotel proprietor on Lochranza, Bute, Scotland; Alister Macmillan (born 1870) died in 1907 in Bute, Scotland); 2 John Mclarty McMillan (born 19 December 1871 Lochranza, Bute, Scotland; source: Scotland, Births and Baptisms (John Mclarty erroneously listed his birth year as 1872); married Isabel May Ewen 1904 British Columbia, Canada; became a manufacturer (cannery business in Vancourver; source: nephew, Ronald Neil Macmillan, "uncle John Macmillan, Vancouver Club", s/s Cedric 1926) in Vancouver, Canada; Capt., WWI, Canada; John Mclarty Macmillan died 12 May 1950 Vancouver, Canada), and 3 Neil McMillan (born 25 February 1874 Lochranza, Bute, Scotland; in 1881 Scotland Census, Neil McMillan born 1874 Kilbride, Bute Scotland, lived with his aunt, Flora McMillan, age 67, in Kilbride, Scotland; Neil Macmillan, age 23, born 1874 Loch Ranza, Bute, earned a second mate certificate #032127 given at port of Greenock on 05 August 1897; Neil Macmillan, 2nd mate, age 24, born Isle of Arran, departed port of Mauritius on the s/s Edenballymore arriving port of Sydney, NSW, AUS on 13 March 1899; possible death: Neil Macmillan died (age 78, born 1874) 1st quarter 1952 in district of Lancaster (Volume 10c, Page 660), county of Lancashire, England).

Margaret Fullerton Mclarty 1840 is a daughter of John Mclarty (John Mclaharty, son of Ronald Mclarty and Isabel Currie, baptised on 14 June 1798 in parish of Kilmory, Bute, Scotland; John Mclarty, mother's maiden name: Currie, John Mclarty died in 1868 in district of Lochranza (556/00 0016), county of Bute, Scotland), and Jean McMurray (daughter of Peter McMurray and Margaret Adie, baptised on 23 September 1811 in parish of Wigtown (901/00 0010 0049), Kirkmaiden, county of Wigtown, Scotland; Jean McMurray Mclarty died (age 57) in 1865 in district of Lochranza (556/00 0012), county of Bute, Scotland).
John and Jean had: 1 Margaret Fullerton Mclarty Macmillan (1840-1876) and 2 Isabella "Bella" Mclarty 1843.

Neil MacMillan 1817 is a son of Alexander Macmillan (probable baptism and parents: Alexander Mcmillan, son of Malcolm Mcmillan and Janet Kerr, baptised on 12 March 1782 in parish of Kilmory (554/00 0020 0135), county of Bute, Scotland; died sometime after 1841 (listed as Alexander Macmillan b. 1782) in district of Lochranza, county of Bute, Scotland); Alexander Macmillan married Catharine Kelso on 24 August 1806 in parish of Kilmory, Shiskine and Lochranza (554/00 0020 0167), county of Bute, Scotland; Catharine Kelso born c. 1786 (daughter of Archibald and Ann Kelso, baptised on 29 January 1787 in parish of Kilmory, Shiskine and Lochranza (554/00 0020 0138), county of Bute, Scotland; Catharine Kelso Macmillan died sometime after 1841 (listed as Cath Macmillan b. 1786) in district of Lochranza, county of Bute, Scotland.
Alexander and Catharine had (all children baptised in Kilmory; all children listed with parents: Alexander Macmillan (or name variant) and Catharine Kelso): 1 Malcolm Macmillan baptised on 01 November 1807, 2 Elizabeth Macmillan baptised on 23 December 1809, 3 Gilbert Macmillan baptised on 09 May 1812, 4 Daniel Macmillan baptised on 26 January 1815, and 5 Neil Macmillan (baptised on 29 August 1817-1891).

Prior marriage of Margaret Mclarty Macmillan, later wife of Arthur Tarleton Macmillan: Margaret Mclarty Macmillan, age 20, daughter of Alexander Macmillan, hotel keeper, deceased, and Mary Macmillan nee Mclarty, married, Patrick Henry Mitchell, age 25, mercantile clerk, son of John Patrick Mitchell, United Free Church minister, and Zoe Blanche Mitchell nee Mason, on 21 July 1915 at the Grand Hotel, district of Hillhead (644/12 0164), Glasgow City, county of Lanarkshire, Scotland, after Banns according to the forms of the United Free Church; Patrick Henry Mitchell (born 1890 in district of St George (685/01 0537), Edinburgh City, Midlothian, Scotland; in 1909 Patrick Henry Mitchell was a clerk (1890 Scotland, father: Rev. John Mitchell) traveling to Seattle, Washington, USA; on 1915 marriage record Patrick Henry Mitchell's address is 42 Inverleith, Edinburgh; in 1926 Patrick Henry Mitchel, 42 Inverleith Row, Edinburgh, was a planter in Borneo; source: 1926 s/s Perseus ship's log; Patrick Mitchell, mother's maiden name Mason, born 1890, died in 1974 in Edinburgh City, Scotland); Margaret Mclarty and Patrick Henry had: Mairi Zoë Mitchell born 20 January 1920 in district of Crieff (342/00 0015), Perthshire, Scotland; Mairi Zoë Mitchell-Macmillan Mason Gibbs Lathbury died 24 April 2007 in England; Mairi Zoë Lathbury buried, with her second husband, Patrick Somerset (Robertson)Gibbs, in Hartley Wintney St Mary Churchyard, Hampshire, England).

Patrick Henry Mitchell 1890 is a son of Rev. John Patrick Mitchell (born in 1853 Glasgow, Scotland; died (age 72) in 1925 in district of St Bernard (685/01 0020), Edinburgh City, Midlothian, Scotland); married, in 1881 in district of St Andrews and St Leonards (453/00 0011), county of Fife, Scotland, Zoe Blanche Mason (born 1857 England; Zoe Blanche Mitchell died (age 83) in 1940 in district of Leith (685/08 0646), Edinburgh City, county of Midlothian, Scotland).

Zoe Blanche Mason 1857 is a daughter of Henry Mason (1831 England-1903 England); married, on 27 April 1856 at St Marys Paddington, London, England,
Harriet Tilbury Wyatt, widow and daughter of John Tilbury (Harriot Tilbury, daughter of John and Ann Tilbury, baptised on 21 August 1833 St Marylebone Christ Church, London, England; Harriet Tilbury Mason died (age 80) in 1914 in district of Galashiels (775/00 0012), county of Selkirk, Scotland).

Mairi Zoë Mitchell was adopted by Arthur Tarleton Macmillan at which time she began using the maiden name of Macmillan.

Mairi Zoë Macmillan married, first, in 1940 in district of Montrose (312/00 0121), county of Angus, Scotland, Robert Thomas Mason (no identifiable data); Mairi Zoe and Robert Thomas Mason divorced by 1948; source: NY Passenger Lists, s/s Queen Elizabeth 1948; no known issue.

Mairi Zoë Mitchell-Macmillan Mason married, second, in 1949 in England, Lt. Col. Patrick Somerset Robertson, later Gibbs born 14 December 1919; birth registered: Patrick S. Robertson, mother's maiden name Butler, 1st quarter 1920 in district of Kensington (Volume 1a, Page 193), county of London, England; Patrick Somerset Robertson was later adopted by his mother's second husband, Maj. Bryan Northam Gibbs (m. 1925, 1897-1965); Patrick Somerset Gibbs died 29 December 1961 at London Airport, London, England.
Mairi Zoë and Patrick Somerset had five children, one deceased as of 1988: Alexander Michael Somerset Gibbs (13 July 1958-13 March 1988).

Patrick Somerset Robertson-Gibbs 1919 is a son of Lionel Gallwey Robertson (1893 England-died in 1926 at the London Coliseum Theatre, London, England) and Lady Rosamond Kathleen Margaret Butler Robertson Gibbs (1899 England-1972 England); Lionel Gallwey and Rosamond Kathleen Margaret Robertson divorced sometime before 1925.

Mairi Zoë Mitchell-Macmillan Mason Gibbs married, third, in 1972, General Sir Gerald William Lathbury (1906 India-1978 England); no issue.

Second marriage: Margaret McLarty Macmillan Mitchell = Margaret M. Mitchell married Arthur T. Macmillan 3rd quarter 1931 in district of St Martin (Volume 1a, Page 1474), county of London, England; Arthur Tarleton Macmillan, barrister (05 December 1889 London, England; source: London, England Births & Baptisms, 1813-1906; Arthur Tarleton Macmillan, son of Maurice Crawford Macmillan and Helen Artie Belles, baptised on 23 May 1890 at Chelsea Holy Trinity, borough of Kensington and Chelsea, London; died Sunday, 11 August 1968 Fakenham, Norfolk, England; source for day: Chicago Tribune, 14 August 1968); Margaret Mclarty and Arthur Tarleton had no issue; Arthur Tarleton Macmillan and his wife, Margaret Mclarty Macmillan Mitchell Macmillan, buried Market Lane Cemetery (Wells Town Cemetery), Wells, Norfolk, England; source: gravestonephotos.com