Since I'm the youngest of 14 cousins, I've watched weddings change, or ruin, relationships over the years. And while it seems horrible to say "his wedding ruined our relationship," it's rarely actually the case. And even when it is the case, it's because the wedding brought out harsh truths about your relationships that you didn't want to admit.
I have a friend whose friendship was ruined over him being a groomsman in his friend's wedding and there being a lack of communication over the groomsman's obligations and about other things, but was ultimately an argument over what each friend expected from each other socially, emotionally, and their relationships with each other's significant others. I'm not sure whose "fault" it was that what happened, happened. But I do know it's super awkward to still be friends with both of them.
The reality of weddings is that they are complicated and for some reason, they bring out the worst parts of the people we love the most. Whether it's a pissing contest between the parents over who has more money/friends/status or it's a brou-ha-ha about how much rap music you want to play at the reception, they can really bring out the terrible parts of people.
My point here is simply that if your wedding is a catalyst for a changed relationship between two people, it is not your fault for having a wedding. There is nothing you did that could cause that - all it caused was these two people to realize something about themselves that makes their relationship different. You will also find out things about yourself that you might not have known before your wedding.* These things might change the dynamic of your relationships with others. But if it is time to end a friendship, it's time. If'it's family, you'll still have to see the person, but you don't have to like them. Don't avoid the inevitable because you blame it on your wedding - that's not fair to your wedding, and it will mar your wedding in your rearview mirror.
How have weddings changed relationships in your life?
* I found I'm not afraid to be selfish or bossy and I'm not ashamed of myself for either of those things. I'm a little ashamed that I'm not ashamed.