Hmm possible but regardless I would be surprised if Meme and Kaido never had a story haha
To me, Kaido owes BM possibly in one of two ways (both are still total guesses don't mind me)
- She saved him and the Numbers from Punk Hazard as children. All of the Numbers are his family. She let him keep them all instead of forcing them on her crew.
- They had a child (Yamato) years ago and BM let Kaido keep the child for x reason.
The first is more likely in my opinion, but both could be entirely wrong.
What's curious is once we see Yamato, people are going to be asking about who the mother is. And I think with this is gonna be pretty important. I've had a few theories on that:
- BM/Kaido obviously
- Kaido/Black Maria, but then Black Maria wouldn't have called him "Bocchan" if he was her son Id say. Who knows
- Kaido/Toki, dark as fuck but maybe Toki lived and they had Yamato lol.
- Kaido/Shimotsuki Clan Mother, this one is my favorite, because Zoro may be related to the Shimotsuki clan in some way, yet I've been wondering how they'd address it. I was making a fun theory how Kaido killed the Shimotsuki clan, took Zoro's mother, and has Yamato (making it that much more personal)