Every family has their own landmines and complex political structures. Every couple has a different relationship with their family and chooses to go along with the politics or not. But sometimes all this causes stress when you feel pressured to invite someone to your wedding that you REALLY don't want to be there.
For my wedding a certain relative always talked down to me, was verbally abusive and just plain mean. I knew if I saw her on my wedding day she'd just say something snarky like
"You could have lost more weight to fit into that dress". But NOT inviting her would make it into this big dramatic thing, so full of wrath that it would become bigger than my wedding. I wish I had the strength no not care, but I did.
Almost every friend who has gotten married has confided in me there was someone at their wedding they felt pressured to invite but loathed to see. The advice I always give it- It's you wedding and in the end you can invite or not invite whom ever you want. But remember, NOT inviting someone can make your wedding all about the exclusion of that relative. For years to come it will be the wedding where "So-and-So" was no invited. If you are fine with that, but all means don't invite them.
However, if you don't want to deal with the drama overshadowing your big day here are a few tips and tricks:
1) Seat them in the back where you will have minimal contact with them.
2) Assign another family member or friend to keep them occupied and away from you
3) Give the unwanted guest a task to keep the busy
4) If you are worried about the guest drinking too much try and limit their intake- limit 2 glasses per guest, or have a dry wedding. Or point them in the direction on the nearest hotel bar and make sure they have a sober designated driver to get home.