Kneass was married to Mary Turner Honeyman Kneass. One of their 6 children, Samuel Honeyman Kneass (1806–1858), was a notable civil engineer and architect, based in Philadelphia. Another, Strickland Kneass (1821–1884), was an engineer. Kneass was remembered as "a warm gentleman of the old-school, who had the rare quality of engaging and winning the esteem and affection of children and youth"