Kline was born in New York City, the son of actors Kevin Kline and Phoebe Cates; he has a younger sister, Greta Kline. Kline's only leading film role to date was in the 2005 film The Squid and the Whale, a part given to him at the suggestion of family friend Jennifer Jason Leigh, director Noah Baumbach's then-girlfriend, now-wife. He was also featured in the Jennifer Jason Leigh and Alan Cummings film; The Anniversary Party, where he played the son of his real father.