Sebastian was married to Kay from 1940 till his death in 1977.
Together with Kay he had had three children. Two of his children are actors: Annette Cabot born in 1952 and Christopher Cabot born in 1955.
As Sebastians father's business failed, Sebatian left school at the age of 14, to help support his family and began working in a garage. It is from those days that he developed a love for cars which remained till his death.