Sir Justinian was married on 9 September 1766 to Susannah Barrett (1744–1823), the daughter of Henry Barrett. They had several children including those who follow.[4]
Reverend Henry Charles Isham (1777–1833) became Rector of Shangton, Leicestershire. The baronetcy passed to his descendants in 1976 when the 12th Baronet Sir Gyles Isham died without an heir.
Betham, William (1801), "Isham of Lamport, Northamptonshire"inThe Baronetage of England, of the History of the English Baronets, and such Baronets of Scotland, etc, Burrell and Bransby, Ipswich, England, v. 1, p. 298-305.