BAV Headcanon/Theory time
OKAY, so this is a post about the Blue and Violet series by SmolBee29 on ao3/amazingdeadfish on tumblr. If you hadn't read it, you should, it's great!
Anyway, the theory is that Xiuying (the Mayor's friend) is Zhuóhuā's (Baihe's mom) sister. Therefore she would be Baihe's aunt.
Here's a drawing of how I think they all look. From left to right it's Xiuying, Zhuóhuā, and Kun (Baihe's dad). I think it would make the most sense for Xiuying to be younger than Zhuóhuā, which is why she's taller. I don't make the rules, younger sisters are taller than older sisters.
ANYWAY, makeshift evidence time.
So, we know in the past the Mayor was the War Chief. During that time, they were married to Xiuying and had Baihe as a kid. We also know that Aigou was Ling's (name of Mayor as War Chief) younger brother. In the present, Aigou could have had a younger brother named Ling, but he died before he was born. This suggests to me that the past lives of these people have similarities to the present lives.
Obviously, Xiuying is not Baihe's mom. So what's the next closest thing? Being Baihe's Aunt.
We also know that Xiuying has siblings/half siblings both past and present by the quotes below. (First one is past Xiuying, second one is present Xiuying)
The reason why I highlighted that part is because Zhuóhuā is an artist. Now I know quite a few artists, and while not all of them have/had dyed hair, a lot of them (myself included) do. So, I think Xiuying is referencing Zhuóhuā here.
I also think this matches up nicely/funnily with the timeline. We know that Baihe was eleven before she got possessed. We know that the Mayor started their journey to becoming the Mayor ten years before LBD was freed. They got into college maybe a year or less into this this timeframe, making Baihe about one or two.
Xiuying is in her 20s, so it would be believable that she has an older sister with a one-two year old.
I mentioned the timeline being funny because of the scenario above. I like to think that the Mayor theoretically had all the piece to suspect that Baihe was Xiuying's niece, but just didn't pay attention/care enough to figure it out. (Also I don't think the Mayor would have known that Baihe's name was Baihe while she was possessed. Honestly, I don't think it would have mattered even if they did).
Mostly though, I just think it would open up a lot of really funny scenarios.
Maybe I'll make a short comic with this idea. IDK. What do y'all think (If you bothered to read all of this)