My sister apologised for his behaviour and assured me she is still attending all parts of the wedding and not to worry
Just read your three threads and literally breathed a sigh of relief at this post. He's definitely trying to at least drive a wedge between you and your sis. And he'll probably start on your mum and sis at some point too. My exP tried the same to me and to his exP and her family, and this guy sounds very similar. Just keep reiterating to your sister that you are always there for her and do want to spend time with her etc. And under no circumstances (as tempting as it would be) say anything that could be construed by her or MrControlling as you badmouthing him. Would not be at all surprised if he's said at least once to her that he thinks you don't like him as part of trying to alienate her from you, and anything remotely negative would be taken as confirmation :(
You've handled this really well! My sis was agonising over who to invite to the ceremony for her wedding due to it being a small venue, so that in itself is already a tough situation for you to have navigated. Incidentally, they had a "no kids at the ceremony" rule too, which makes sense tbh since ime wedding ceremonies can be really boring for kids even when they have a part in it...
Hope your big day goes off without a hitch (well, except the one that's supposed to happen anyway ;) )