Kar was married to Princess Maria Sergeyevna Khovanskaya (1756-1833), and together they had four children: Ekaterina, Anna, Aleksey, and Sergei (died 1869). After the death of her husband she retired to a monastery in Kaluga. Both of his sons entered the military and fought against Napoleon's Invasion in 1812. Aleksey would lose a leg at Berezina while commanding an artillery battery, and Sergei would become a decorated cavalry officer in the following campaigns.