Disclaimer: tabathafaye, I am in no way shape or form implying this is the situation for you. It sounds like your ILs really do like you and the bride was a bitch. It just reminded me of something that happened at my wedding.
So my BIL and his wife have been together the same amount of time as DH and I. After 2 years DH and I are getting married. They are living together but not engaged. MIL, sFIL, FIL, and sMIL do not like SIL. At the time of our wedding they REALLY didn't like her. I mean like they were actively trying to break them up. FIL even offered BIL $50k and a new truck to leave her.
Again they are not engaged.
I wasn't sure how MIL and FIL wanted to handle family pictures and I didn't want to get involved. I knew there was (and is) bad blood with this woman and there are step brothers and step sisters all over the place. I told them to get me a list of people they wanted in pictures. If they wanted different family groupings, if they wanted just the parents and DH, whatever. They each gave me lists of several shots. Not one of them included SIL.
Until this moment it hasn't really crossed my mind that her feelings might have been hurt. I kind of feel bad, but she's also kind of a bitch. If she does feel bad I hope she blames me and not the parents though.