Family issues

My 9 year old daughter is spending the last few weeks out of school with my parents. My brother and his wife have 3 kids and my sister in law said today she wanted to take her kids over to my parents to play with my daughter. I told her I don't fee comfortable with that since there is COVID and told her it's best to not go over because of it. And of course she had to text my mom bitching about how I don't want her kids around mine daughter right now. Her kids literally stayed sick ALL winter, like every other week one of them was sick with something, they live with my sister in laws mom right now, they have 9 people living in that house. She told me the kids never go anywhere. But they do, every single person in that house except her mom are always out and about, never home. They could have easily gotten the virus and took to home and they could be sick and not even know it because alot of people aren't showing symptoms and have it. She got pissed and said I act like they aren't family. That's not even the case, I'm just looking out for my daughter and her health. My parents haven't left the house at all since all this came around because my dad has heart failure so he's high risk. We haven't left the house either so that the only reason she's at my parents right now. Anyway, my mom was like "you know, they are your family, they're are your nieces and nephews" yes I know but honestly ever since my brother married my sister in law, he changed. They are always always talking shit about people behind their backs, including my parents and then kids ass later like nothing has happened. My brother treated my like I was a no body back in January and I haven't spoke to them since, until today. I texted to see how they were and then all this bullshit happened. My mom was like "I hate seeing my kids not get along" yea well tell your son that because he started it all by treating me like a no body and never once said he was sorry for it. And here i am getting bitched at by my mom like I done something wrong. I've tried to talk to them and be the better person a few times since January and they go back to being assholes again shortly after. I don't know, I'm just sick of it all. Sorry if this was all over the place, hopefully it made sense at least. Rant over.