The birth of Victor is definitely out of whack. The official timeline states that he was born in 1949. This implies that Connie's first pregnancy ended up in a miscarriage, or that she gave birth to an unknown first child. Due to Carlo beating her while she was pregnant, a miscarriage could have been plausible, but I believe this isn't mentioned in the novel. Maybe it's different in the film as the novel also doesn't mention that Michael and Kay had a daughter or that Sonny impregnated Lucy Mancini.