The son of actor and theatre producer Chandler Cowles, he was born in New York City.　　He was first married to Kathleen Dezina, an actress, known for All My Children (1970); but the couple divorced. Since 1983 he has been married to actress Christine Baranski with whom he has two daughters, Isabel (born 1984) and Lily (born 1987). In a New York Times profile of his wife, he is described as “the black sheep member of a family with ties" to Drexel banking and the Cowles Publishing Company.He was an enthusiastic motorcycle rider.