He married firstly Sarah, daughter of Isaac Waldo of
Streatham, and secondly Elizabeth Gibbes, daughter of John Gibbes, merchant, of London and
Instow, Devon. His youngest son was the botanist
John Sibthorp (1758–1796), who continued the
Catalogus Plantarum. His oldest son,
Humphrey, was a Tory MP for Lincoln. His daughter, Sarah, married
Montague Cholmeley (b. 8 Jul 1743 - d. 9 Sep 1843) and was the mother of
Sir Montague Cholmeley, 1st Baronet. Another daughter Mary Elizabeth was the second wife of Sir
Thomas Sewell,
Master of the Rolls. ==References==