Tough. Well Super Mario wiki has mentioned that is a mystery, because the website said Bowletta, their mother, never said `Koopalings come her' to Bowser Jr, either Junior doesn't share a mother and he never listens to Bowletta, 또는 his real mother is dead
I think (read somewhere) that 'cause of Cackletta's Bowser body possession,an egg was made. It was a side effect of the possession. So,it's probably Cackletta his mother... If 당신 think about,you'll see Superstar Saga and Sunshine (Junior debut) are the same 년 (at least in Japan,2002/2003.)