Baldwin was born April 3, 1958, in Amityville, New York, and raised in the Nassau Shores neighborhood of nearby Massapequa, the eldest son of Carol Newcomb (née Martineau; born 1930) and Alexander Rae Baldwin Jr. (October 26, 1927 – April 15, 1983), a high school history/social studies Teacher and football coach. He has three younger brothers, Daniel, william, and Stephen, who also became actors. He also has two sisters, Beth and Jane.