His father was
Sir John Jacob, third baronet of
Bromley, Middlesex (c.1665–1740) and his mother was Dorothy (c.1662–1749). Sir John served in the army from 1685 to 1702, seeing action at the
Battle of Killiecrankie and in Ireland. Following his father, Hildebrand served in the army until at least 1715, then in 1717 he married Meriel, daughter of another baronet, Sir John Bland of Kippax-Park, Yorkshire. They had a son, also Hildebrand, and a daughter, Anne They made their home at
West Wratting Park, Cambridgeshire. He never succeeded to his father's seat, dying in 1739, a year before Sir John. His son Sir Hildebrand Jacob (1717 or 1718–1790) succeeded Sir John at his death on 31 March 1740, becoming the fourth baronet. ==
Brutus the Trojan==