Family Drama - Who do i invite and where do i put them?!

The good news is that you don't have to worry about the seating chart until RSVPs are in, which is usually a month prior to the wedding date. As far as who to invite, I have a few thoughts. 1. Great aunt doesn't get to dictate guest list. Start setting those boundaries because this behavior tends to escalate. 2. Make sure to set a budget if you haven't already, and that will help you figure out how many people you can invite anyway. Catering/rentals/etc are per person, so you have a finite amount of people you can invite within a budget. Start compiling a list of all the people you and your partner really want at the wedding. Plus ones are for truly single guests and not required. However, couples are a social unit so you should count those partners in your headcount. Your great aunt's cousin's neighbor's friend does not need come to your wedding, no matter how close your great aunt is to them. If you don't know/like someone, they don't need to be on the guest list.

Regarding the great-aunt trying to control things, put your foot down now, or else things will get worse. Do not accept guest lists/planning demands that she tries to send you. Each attempt should be countered with a polite response along the lines of “thanks but my FH and I have decided we will be planning and paying for the wedding ourselves to our own liking”.

As for whether to invite the different family members, this is a decision that will need to be made by you and your FH based on how you feel about each person and whether they are someone you can’t imagine your wedding day without. If there are any not invited and other family members complain, remember, no pay, no say. You’re the final decision maker.

If you do end up inviting quarreling relatives, I'd just suggest seating them on opposite ends of the room. But seating charts should not be worked on until you have all the RSVPs in (usually a few weeks before the wedding), so who knows, maybe one side will decline and you don’t have to worry about that. Best to wait until responses are in.

We didn’t invite anyone that we didn’t have relationships in the past several years. Just because they are family doesn’t mean you have to invite them.
As for seating, there were guests who weren’t speaking or fighting on our list. I didn’t worry about that as it’s not our problem. They are grown adults and can sit at the same table. I put them together and there weren’t any problems.
Seating charts will change often do it last like Erin said.

Looks like you have a looooong time before you need to sort that out. Sounds like it will be a pain though, and I'm sorry about that for you.

I would put up big boundaries with your great aunt now. "Sorry we can't accommodate those guests". Don't give excuses or reasons, because she will try to "solve" the problem so she can get the people invited. Don't give an inch or you'll be spending the next almost two years dealing with her. I would stop discussing wedding planning with her entirely.