They sound very strange, to say the least. You can’t change them so I suggest you don’t think about them or how they behave. It’s on them.

And welcome to the club. My sister in law (brothers wife)is also rude (in a subtle way, not like putting fists in peoples faces). My husbands brother in law (his sister’s husband) is almost grotesquely rude. Like last time we saw them he didn’t turn his head to even say hello to us. He eventually spoke to me (barely) but never spoke to my husband. He’s been always this way, rude. He is rude to everyone in my husbands family, not just us. Heck, my own father is very rude to people.

That’s how some people are. All you can do is to keep seeing and talking to them to the most minimum possible (if can’t stop completely). And try to not think about them. I’d not bother trying to change them. Just distance yourself from them if you can