Fortescue was the eldest son and heir of Arthur Fortescue (1622–1693) of Penwarne, Mevagissey, Cornwall and of Filleigh in Devon, and his wife Barbara Elford, a daughter of John Elford of Sheepstor in Devon.[2]
Arms of Boscawen: Ermine, a rose gules barbed and seeded proper
Firstly on 19 October 1692 to Bridget Boscawen (d. 1708), a daughter and eventual heiress of Hugh Boscawen, (1625–1701) by his wife Margaret Clinton, a daughter of Theophilus Clinton, 4th Earl of Lincoln, and one of the co-heiresses of the Barony of Clinton upon the death of Edward Clinton, 5th Earl of Lincoln in 1692. Bridget was the only child (out of eight sons and two daughters) to outlive her father Hugh Boscawen, (1625–1701); she brought money with her marriage thus increasing Fortescue's fortune. By Bridget Boscawen he had four children as follows:
Margaret Fortescue (d. 14 March 1760), died unmarried.
Arms of Aylmer: Argent, a cross sable between four Cornish choughs proper[7]
Secondly, after 1708, he married Lucy Aylmer, a daughter of Matthew Aylmer, 1st Baron Aylmer (circa 1650–1720). A stone relief-sculpted heraldic cartouche erected by him survives above the entrance door of his seat of Ebrington Manor House in Gloucestershire, displaying the arms of Fortescue impaling Aylmer.[8] By Lucy Aylmer he had two further children:
St John the Baptist Church, Hagley, memorial statue to Lucy Lyttelton (née Fortescue, died 1747), the first wife of George Lyttelton, 1st Baron Lyttelton
St John the Baptist Church, Hagley, memorial inscription to Lucy Lyttelton (née Fortescue, died 1747)
St John the Baptist Church, Hagley, information panel at statue to Lucy Lyttelton (née Fortescue, died 1747)