William Cowper was born in about 1665. He
was the son of Sir William Cowper, 2nd Baronet, of Ratling Court, Kent. , a Whig member of parliament of some mark in the two last Stuart reigns. His younger brother, Spencer Cowper (1669 - 1728), was tried for the murder of Sarah Stout in 1699, but was acquitted; the lady, who had fallen in love with Cowper, having in fact committed suicide on account of his inattention.