Well, first off, here's what I think.. Baby Bowser is Bowser when he was young, but Bowser JR. is Bowser's actual son. Where he came from is unknown and shoddy, and as for the seven other Koopa Kids, my idea is that Bowser came across seven eggs abandonded somewhere, and he took them home, and raised them up to be who they are. Some other theories can arise out of that, such as Morton Koopa, Jr.. If there's a "JR" in his name, then that means there's gotta be a senior in the royal Koopa family somewhere, unless Bowser's real name is Morton, but due to embarrassment, he changed it to Bowser, which could've been his middle name.. Morton Bowser Koopa.. it could work.