Series III. Phillips Family Relatives, 1636-1897, contains materials created by a distant ancestor, Reverend George Phillips (1593-1644), a relation from Watertown, Massachusetts, Wendell Phillips (1811-1884), and two of Stephen C. Phillips' sons, Willard Peele Phillips (1825-1901) and George William Phillips (born 1827).

Subseries A. Reverend George Phillips (1593-1644) is limited to three items. Two are undated theological notes and drafts of sermons, and the third is a reproduction of a letter to John Winthrop, governor of the Massachusetts Bay Colony.

Subseries B. Wendell Phillips (1811-1884) includes a brief letter (circa 1870) to W.K. Heinzen regarding the Franco-Prussian War.

Subseries C. Willard Peele Phillips (1825-1901), includes correspondence received from W.H Osborn concerns coastwise trade and the financial affairs of Stephen C. Phillips.

Subseries D. George William Phillips (born 1827), includes correspondence which is concerned with insurance and financial matters, and reveals George's close financial relationship with his brother Stephen Henry Phillips.