My sister in law is my matron of honor. (have known her 20 years as she & my brother started dating in 10th grade) Her parents are invited (they have is down to their cottage, are very close with my parents). My issue is my sister in law has 3 sisters, 1 of whom I am closer with (she helped me during a very difficult time, we've done stuff outside of family time & I take her zumba & boot camp classes). I definitely want to invite her but as far as the other 2 sisters, I am friendly with, but not nearly as close to. I do see everyone every 5-6 weeks for book club plus my nephews' birthday parties during the year. I'd be happy to invite everybody but not sure if they would be offended or if it's against etiquette if they don't get an invite. (The one sister got remarried last summer & I wasn't invited, nor my parents, not that it matters I guess) What should I do?