Francis had been a younger brother of William Seymour, 2nd Duke of Somerset.
[1] He married firstly, on 4 April 1632,[1] Mary, daughter of Thomas Smith of Soley in Chilton Foliat, a village northwest of Hungerford.
One of his notable descendants, his three times great-grandson, was the chemist and mineralogist James Smithson.
His daughter, Honora Seymour, married Sir Charles Gerard, 3rd Baronet.
[6] Charles Seymour was succeeded in the barony by his elder son, Francis.