I call him the runt/ the fat one/ normal one out of the two other kids-he is another inside joke-that turned into a real thing ordeal and you can blame the people I associate with a lot lol.
Disclaimer : *this is an AU where Bowser Jr and Toadette are fully grown adults I do not ship them in canon
Name : Blaise
Nicknames : Big Mac (because Toadette likes them mcdonalds hamburgers), fatty,the fat one, runt (mostly by Phoenix and Bubbles)
Age : Child form 3-6 Adult form : 19-23
Species : KoopaToad
Gender : demiboy (he/him pronouns)
Parents : Bowser Jr (Father) Toadette ( Mother)
Siblings : Bubbles and Phoenix

Other stuff
- Unlike Phoenix, Blaise is mainly a toad for the most part inheriting most of his mother's heritage
- He came specifically 3-4 years after Phoenix, after Toadette managed to get out of her postpartum depression when she unexpectedly came pregnant again to Toadette's own luck.
- His parent's don't really have interest in making him a future king hence why he's mainly called the "runt" and is considered the normal one of the other two
- He's considered less aggressive than Phoenix, but also a lot less nicer than Bubbles so basically he has Toadette's personality (think of super mario maker 2 story mode)
- The only reason he is considered pretty fat/bigger than the other two kids is he was pretty much born much bigger than expected ethier due to one of the side of effects of being a koopatoad or one of his parents genes.

Drawn in Photoshop CC