<human>: Summarize the given text in a few sentences.

Me and my SO have been together for 2 years, and will be getting engaged soon. We'll be looking to get married within a couple of years. However, we have quite a few problems with his family and what to do about inviting them to events etc.

Before I showed up, SO and his mother were not close, spoke very infrequently. When I appeared, she decided she hated me and SO decided that she could fuck off. Now they're estranged. Anyway, his sister still talks to him but refuses to invite me to any of her events like parties etc. Which means he refuses to go, because he says we come as a pair, plus she expects her boyfriend to get invited to whatever she goes to. So I have never met the sister.

Anyway, that's the situation. After being snubbed repeatedly by the sister, I decided I don't want her at any of my events e.g. a wedding - firstly because I don't know her at all, and secondly because she is being so rude towards me. Obviously the mother will not be invited, because SO hates her. But I also don't want the sister there. If we don't invite the sister, it will definitely look weird to his other family members who do come, and will be making a big statement - and will probably screw up their relationship permanently.

We've discussed it and he's on the fence about it, basically he doesn't want her there particularly, but feels like he should invite her. I don't think she would try to screw up the wedding, plus my brother would stop her doing anything bad anyway. What is the best course of action here?
<bot>: SO's partially estranged sister doesn't invite me to anything, we're discussing wedding plans and I don't want her there. He feels like he has to invite her. What do?