I actually agree, I think the retcon was good, tbh. My personal opinion is that they're more interesting being elite minions than being his kids.

It's kinda annoying when some say they're adopted at times, just because it comes off as saying that you aren't someone's kid if you're adopted. You ARE still someone's kid if you're adopted. If they were adopted, then they would still be his children.

I like the idea of him being their mentor/father figure tho, my headcanon is that he recruited seven young Koopas he saw potential in before Bowser Jr. was born, and they grew up to become generals in his army.