Check out Dr. Wily's video or this.
https://www.youtube.com/watch?v=aRXu0vR4F10
https://www.eurogamer.net/articles/2012-09-25-miyamoto-doesnt-know-who-bowser-jr-s-mom-is-but-explains-marios-hair-colour
So I just wanna say even if they are not related to Bowser. Nintendo does claim they are adopted to him. I just wish he call em more koopalings than minions but that's just me. They support Bowser Jr as well.
What do you guys think of Toadette becoming Peachette? Some people think the two are the same but most know that's not true including myself. Peach was never a Toadette in the first place.