Not having any issue by his wife, he adopted Constantine, her nephew, and at his death bequeathed to him the bulk of his fortune. He is said generally, in the genealogies of the family, to have been Phipps's own son; but in "The Life of his Excellency Sir William Phipps, Kt., late Captain-General and Governor-in-Chief of the Province of Massachusetts Bay, New England, 1697," which was published during the lifetime of his widow, it is said distinctly, "not having any child of his own, he adopted a nephew of his wife to be his heir." Sir Constantine Phipps, his nephew, who assumed the name of Phipps on inheriting his uncle's property, became Lord High Chancellor of Ireland, was knighted, and died in 1728. William, his son, married the Lady Katherine, daughter of James, fourth Earl of Anglesey, by the Lady Katherine Darnley, a natural daughter of King James II., who re-married John Sheffield, Duke of Buckingham, Duke and Marquis of Normandy, and Earl of Mulgrave. Constantine, his son, who died 1780, was created Baron Mulgrave of New Ross, in the Peerage of Ireland, in 1768. Constantine, his son, second Baron, was the famous navigator, who made a voyage of discovery into the Arctic regions, and was, in the Pitt Administration, Joint Paymaster of the Forces, a Lord of Trade, and a Commissioner of the India Board. He was created, in 1790, Baron Mulgrave, of Mulgrave Castle, in the Peerage of England, but, dying issueless in 1792, that title expired. His portrait may be seen in Greenwich Hospital.