His family and his ex

Ci

So I’m in a relationship with this guy we’ve been together on and off since 2012. However, we just officially committed to each other with nobody else in the picture in 2018. He has an ex he messed with in 2013 that had 2 kids. After a while they broke up and she got married and had another child by her husband.

The problem is his 3 sisters continue to allow her presence in the family and my boyfriend isn’t okay with it or her husband and neither am I. The sisters say they don’t like her, she causes drama etc. and says I’m the best girlfriend he ever had, but to me it looks like they’re playing sides.

So, apparently the sister who lives down the street has been babysitting her kids but she had to work. And she asked the sister who stays in the house with me and my boyfriend to keep them and their mom (his ex) we’re going to bring them and pick them up.

Is it weird and disrespectful that his sister kept her 3 kids in the house that me and my boyfriend stays in knowing that me and her had issues before and knowing that he doesn’t want to have any dealings with her period?

Why does his sister’s think it’s okay for his ex to be around this family period when he made it clear to them that he doesn’t want anything to do with her?

I’m confused. It’s a lot of fake shit happening..