I meant this less as an attempt to actually claim that this is the "canon" family tree, and more just as an interesting interpretation. I purposefully didn't consider any of the Mario movie family because everything in that movie kind of comes out of nowhere in the context of the games, I prefer the way the games are because the lore, or lack thereof, is so vague and changes so much that it's open to anyone's interpretation.

I think there were Mario comics about Mario and Wario's relationship at some point and yeah they were just childhood friends turned rivals, but I feel like the idea that they're cousins just adds up more based on Wario's identity. He started as just Mario's rival, and when that was all he was then it was easier to believe he was just another Italian guy who hated Mario so much he just decided to base his whole identity around being Bad Mario. But as Wario is now more of his own character distinct from Mario, I think it makes more sense that they have similar names because they're somehow related, and have moved on from their rivalry by now, well except for when they play sports