You are planning your wedding…SO…invite the people that you want there. Plain and simple. Who the F cares if people are upset. If you cared enough about those people you would have invited them. Don’t feel guilty. It’s an expensive event AND it’s about you two, not your second cousin, per se.
If people aren’t understanding of that, TRUST ME, you didn’t want them around any way.
PLUS, do keep in mind that you are going to have to account for “plus 1s”. Yes, people will start dating right after you send out your invites. Months later when your wedding approaches, they will still be in that relationship. Since you are close to this said person, there is no way you want to make them come to a romantic event and not have their significant other to dance with. Do keep that in the back of your mind.
PS. Go ahead and use the main image above, my table seating guide, when planning your tables. It is REALLY helpful. (The coordinator at my venue loved it so much that he asked for the file and gave it to several of his clients :))