Francis was the eldest surviving son of
John Fortescue of Salden at
Mursley and his wife, Cecily Ashfield. His brothers were
William Fortescue and
Thomas Fortescue II. In 1589, he married Grace Manners (d. 1624), daughter of Sir John Manners of
Haddon Hall, second son of
Thomas Earl of Rutland, and of
Dorothy Vernon daughter and co-heir of Sir George Vernon. They had at least one son, his heir, John. A daughter, Dorothy Vernon (d. 1650), married Sir Robert Throckmorton of
Weston Underwood, Buckinghamshire and
Coughton Court. ==Career==