McKean was born October 17, 1947, in New York City, the son of Ruth, a librarian, and Gilbert McKean, one of the founders of Decca Records, and was raised in Sea Cliff, New York, on Long Island. McKean is of Irish, English, Scottish, and some German and Dutch, descent. He graduated from high school in 1965. In early 1967 he was briefly a member of the New York City "baroque pop" band The Left Banke and played on the "Ivy, Ivy"/"And Suddenly" single.