Mary Gladys O'Sullivan was born in 1889 Ormskirk, Lancashire, England to James O'Sullivan and his wife, Ellen Hanrahan. Both of her parents were immigrants from Ireland, her father working for the Office of Inland Revenue. Prior to her marriage, her mother was a Principal at St. Peter's in Stalybridge, England. Mary Gladys typically called Gladys or Glad was the fourth of nine children. Her siblings were:
1. John Francis O'Sullivan 1885-1913 buried St. Mary's Catholic Church Kensal Green Cemetery
2. Agnes Genevieve O'Sullivan 1887-1971 married Gilbert Cameron-Mowat moved to Scotland
3. Catherine Kathleen O'Sullivan 1888-1896 buried at Ford Cemetery in Bootle, Lancashire, England with maternal grandparents - James Hanrahan and his wife Marie Fleming
4. Mary Gladys
5. James O'Sullivan 1891 - 1894 Family history says he died when he fell off the bed during nap time
6. Luke Aloysius 1893- ?? buried in Enfield, Middlesex, England; served in the Royal Navy during World War II
7. Twins: Ethel Ann 1895-1977 buried Enfield, Middlesex, England married first to Patrick Welby who died in 1932 in Singapore and secondly to Oratio Vagnone who was taken Prisoner of War by the Japanese during the second World War
8. Twins: Horace Alexander O'Sullivan 1895-1917 died in the First World War buried Ecoivres Military Cemetery, Mont-St. Eloi, Pas de Calais. He was studying to become a Catholic priest.
9. Aileen O'Sullivan 1901-? married William Phipps moved to Australia

Mary Gladys' first finance died in the first World War.

Believing she won't marry since most men her age had died in the First World War, she married her cousin, Charles Edward Bertrand who was 8 years her junior. They wed in 1921 in Oslo, Norway. They had four children: Mary Gladys born in 1921 and Kathleen Francis born in 1923 both in London. They moved in 1926 to the United States where Charles Philip was born in 1927 and Joan Francis in 1931 both in New York.