Bobby Darin (born Walden Robert Cassotto) was an American singer, songwriter, and actor of film and television. He performed in a range of music genres, including pop, rock'n'roll, folk, and country.
Bobby Darin married Sandra Dee in 1960. They met while filming Come September (which was released in 1961). On December 16, 1961, they had a son, Dodd Mitchell Darin (also known as Morgan Mitchell Darin). Dee and Darin officially divorced on March 7, 1967.
Correction: As you've noted, "Bobby Darin" was a stage name. The correct name at birth, as you've noted, was Walden Robert Cassotto - that's what should be listed as his name. "Bobby Darin" can be listed as an alternate or "preferred" name.