John Boston was a younger brother of Anna Mae Boston who married John Rapp. John Boston's wife, Elizabeth Rapp, was John Rapp's half-sister. Here is his family:

Children of Heinrich and Elizabeth Knack Boston:
Anna Mae (1856 – 1940)
Ida (1858 – 1931)
Louis (1859 – 1933)
Otto (1861 – 1944)
Emilie (Amelia, Mealy) (1863 – 1942)
Rebecka (Bertha E) (1865 – 1914)
John (1866 – 1917)
Frederick (1869 – 1934)
Edward (1870 – 1959)
Henry (1875 – 1960)
Lena (1879 – ) ???
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

1870 United States Federal Census
Name: John Boston
Birth Year: abt 1867 in Illinois
Home in 1870: Minonk, Woodford, Illinois
Race: White
Post Office: Minonk
Household Members:
Henry Boston 42
Elizabeth Boston 36
Ida Boston 12
Louis Boston 11
Otto Boston 9
Amelia Boston 7
Bethe Boston 5
John Boston 3
Frederich Boston 1
Baby Boston 2/12 [Edward]

1880 United States Federal Census
Name: John Boston
Birth Year: abt 1867
Birthplace: Illinois
Home in 1880: Minonk, Woodford, Illinois
Race: White
Relation to Head of House: Son
Father's Name: Henry Boston b. Brandenburg
Mother's Name: Elizabeth Boston b. Brandenburg
Occupation: At Home
Household Members:
Henry Boston 51 (farmer)
Elizabeth Boston 45 (keeping house)
Anna Boston 24 (works at home)
Ida Boston 22 (works at home)
Lewis Boston 21 (farmer)
Otto Boston 19 (farmer)
Mealy Boston 17 (works at home)
Rebecka Boston 15 (works at home)
John Boston 13 (at home)
Fredrick Boston 12
Edward Boston 10
Henry Boston 5
Lena Boston 1

1900 United States Federal Census
Name: John Boston
Birth Date: Dec 1866 in Illinois
Home in 1900: Minonk, Woodford, Illinois
Relation to Head of House: Head
Marital Status: Married
Spouse's Name: Lizzie Boston
Marriage Year: 1892
Years Married: 8
Father's Birthplace: Germany
Mother's Birthplace: Germany
Occupation:
Household Members:
John Boston 33 [Dec 1866] (farmer)
Lizzie Boston 25 [July 1877]
Lena Boston 5 [Aug 1884]
Louis Rapp 18 (nephew) [Jan 1882] (farm laborer)

1910 United States Federal Census
Name: John Boston
Birth Year: abt 1866 in Illinois
Home in 1910: Minonk, Woodford, Illinois
Relation to Head of House: Head
Marital Status: Married
Spouse's Name: Lizzie Boston
Father's Birthplace: Illinois
Mother's Birthplace: Illinois
Neighbors: Appearing on the same census page were Conrad Bonk, Lena Bonk (Elizabeth's sister), William Bonk and Mary Bonk.
Household Members:
John Boston 44
Lizzie Boston 38
Lena Boston 16
Ester Boston 2/12

I believe he died in Limestone Twp., Peoria, Peoria, Illinois. (source: "The Fort" in Lexington, McLean, Illinois)