I am searching for information on my ancestors in the Sackville line. Can you help me get on the right track?

Here is what I know thus far (from 1880 census):

Joseph Sackville
Estimated birth year: 1850
Birthplace: New York
Home in 1880: Philadelphia, Philadelphia, Pennsylvania
Occupation: Bar-Keeper
Spouse's name: Margaret (Cox) Sackville
Father's birthplace: ENGLAND
Mother's birthplace: IA

Margaret (Cox) Sackville
Estimated birth year: 1854
Birthplace: Pennsylvania
Spouse's name: Joseph Sackville
Father's birthplace: IRELAND
Mother's birthplace: PA

Children:

Elizabeth Sackville
Estimated birth year: 1876
Birthplace: New York

Joseph Sackville
Estimated birth year: 1878
Birthplace: New York

William Sackville
Estimated birth year: 1879
Birthplace: New York