I feel like I'm obligated to ask my fiance's sister to be a bridesmaid, but there's a couple of reasons I'm hesitant.
1) Our personalities clash. We started off not having a great relationship because I started dating my fiance at age 20 (he was 21) and I think she viewed us as immature and stupid. Plus, she lives across the country so I only see her once a year for a couple of days. I'm now 25 and our relationship has definitely gotten better, but we're still not close. I still think she's condescending to me (and my fiance) since I'm so much younger
2) There's a big age difference between her and me/other potential bridesmaids. As I said above, I'm 25. The other potential bridesmaids I'd ask are all 25-27 (and all still in graduate school of some sort). She's 36 or 37 and has kids so she's in a totally different stage of her life
3) Everyone else I would be asking lives on the east coast within 3 hours of each other and our wedding would be on the east coast, since our families are from here. She moved to the west coast years ago. Not sure if this matters at all
The reasons I feel like I should ask her:
1) She's going to be my future sister in law, and even if we don't see each other frequently obviously I want to have a friendly relationship even if we're not super close
2) For her wedding, my fiance was a groomsman on her husband's side. IMO this is different than our situation because this was before her and her husband moved across the country, so my fiance actually saw him frequently
3) My fiance will probably have his brother as his best man so it'd probably be rude to not include her as well
TLDR: I think I should have her to be nice/PC, but I don't like her that much and think she's controlling/condescending to me since I'm so much younger. Advice?