Sonny Corleone is the oldest son of Don Vito Corleone, and would have been the successor of him if Sonny wasn't shot and murdered on the causeway by Don Barzini's men. Sonny was only going that way because his brother-in-law Carlo had been beating his sister Connie around for not being a "good wife". Sonny was going to put a stop to it but was stopped, and this wall planned. Carlo had been working secretly with Barzini so that Sonny would be killed and the Corleone Family would be weak and easy to win a mob war. Sonny has two other brothers, Fredo and Michael..and his sister Connie. Sonny was always the most aggressive out of all the brothers. When his father was shot in the street and Fredo didn't do anything, he was very furious and wanted to take the gunners out that instant. He had also cared about whatever his brothers would do in life. When he heard that Michael Corleone was going to be fighting in WWII, he was very angry and couldn't believe he was going to tell their father that on his birthday. Sonny had a wife named Sandra, but that didn't stop him from dating Lucy Mancenelli. Before he died, he had left Lucy pregnant and eventually that son would be in the 3rd movie. His name was Vincenzo.