Jesus ultimatum

[Angrboda]

But now I have another problem. I am really on the fence on whether or not I should sever all ties with my sister and her husband/my best man at my very own wedding, or if I should be a supportive brother even though I know she has done something that I find fundamentally immoral.

Love them though you know they be wrong. It is the only sane and compassionate course. (Of course, love can demand some hard choices. Like cutting off relations to influence the other, or letting a child make its own mistakes. Yet it sounds like your will to isolate sister and brother-in-law is controlling in the same sense as his actions. When in doubt, do not act. Time is often a great aid to the ineptness of our petty schemes.)