First some background on the situation. My FI is one of 6 children (4 sisters, 1 brother) so needless to say I knew going into our relationship that things weren't always going to be smooth sailing...
FI and I knew very early on we wanted to get married (we got engaged 10 months after dating), so he really encouraged me to get close with his mom and sisters. I got along great with his mom and 3 of the 4 sisters. The youngest has never liked me since day one, despite my best efforts to connect with her.
Fast forward through the youngest's countless passive aggressive (and some not so passive) Facebook statuses, Twitter posts, snide comments at family events, and even a full-blown temper tantrum at a birthday party about what she finds wrong with me. Despite her best efforts I still got along well with FMIL and the other 3 FSILs. They were all very supportive of our relationship, called me their sister, I knew they were going to be bridesmaids at our wedding.
A few months ago there was a very big fight between FI, FMIL, the problematic FSIL, and a FSIL I had always been close with. FMIL and FSILs essentially attacked FI about everything they found wrong with me and that I was ruining the family (never mind the fact that FI and I bent over backwards to help when relatives died, when FSIL was hospitalized after a suicide attempt, when FBIL's girlfriend broke his jaw, and more). FI, being the amazing man that he is, told them where they could stick their opinions and we declined seeing them over Christmas.
After a month or so the entire situation was swept under the rug with a half-hearted apology on FMIL's part and a very confusing, crying apology from the FSIL I had been close to. Problematic FSIL continues to act like a 13 year old despite the fact that she is 22.
FI has 2 other sisters, one who lives in Missouri and one who is married with kids. The FSIL who lives in Missouri is fairly separated from the drama and has always been kind and polite to me. However, she is very close to the youngest FSIL and I am very concerned that though she is nice to my face, she feels the same way as the youngest FSIL does about me. The oldest FSIL and I are very close. She and her husband have done nothing but love FI and me, support us, and encourage us to ignore the drama.
Finally to the point of this post: do I have to include FI's sisters in my wedding? The last thing I want to do is cause more drama or regret the decision a few years down the road, but I don't trust any of them (oldest FSIL excluded; she is a bridesmaid, her husband is an usher, and her sons are the ring bearers). My worry is that they and FMIL will continue to cause drama and be toxic during what is supposed to be a very happy time. I also worry that on my wedding day they will purposefully cause issues. A bridesmaid is supposed to be a person who loves you and supports your marriage; at the end of the day I'm just not sure I want these women standing up with me.