Husband and sister dont get along

My husband and My Sister don’t get along that’s the crux of the issue. My husband is best friends with my sisters husband. When I got married my husbands freind let’s call him Peter saw my sister Jane and they fell inlove and got married 2 years after us, they have a baby together. Fast forward a year into their marriage things don’t go well, the usual couple stuff, Peter calls my husband and tells him what’s going on, his side. Jane my sister calls me and tells me what’s going on her side obviously. I try best I can be to be neutral and yes in most cases jane my sister is wrong and I call her out on some things and try to share with her how to best resolve things and how to “fight fair” and yeah hubby is also convinced my sister is wrong most of the time but uses this negatively sometimes, he feels terrible for his freind. I love my sister and even though she may be wrong I also want their marriage to work, so does hubby but him and I end up arguing a lot about Jane and Peters issues. It gets so bad that I can’t stand talking about them and listening to my husband calling my sister out on things, I’m very defensive and protective of her, I highlight to him that even though they told me stories about some family members and I don’t agree with how some ppl behave I never ever talk bad about them or talk negetively of them to him, he must stop talking negatively about my sister anyway we end up agreeing that we won’t talk about them and their issues anymore.

Fast forward again my sister talks to me and says that he doesn’t get along with my husband, she feels he has too much influence over Peter, Peter doesn’t listen to anyone except my husband. She feels hubby has a negative perception of her and he might influence peter to leave. Anyway hubby also talks to me that he doesn’t get along with Jane because she treats Peter like shit and he loves peter they’ve been best friends since childhood and he won’t let anyone break their friendship Peter is like a brother to him.

Anyway it’s gotten so bad that my sister avoids being where my hubby is, and whenever she’s upset about something like not being added to a chat group by my husband (which I called him out for and feel he should apologise) she bars everyone in her family to come to the function we were planning, which is upsetting to me because I want them there.

How do I address this tension and dislike of each other between my husband and my sister ?