What to wear to a friend's wedding?

[Liam]

You are lucky about that. My future sister in the law knew I'm a full-time kilt wearer. Yet, I'm banned from wearing my kilt to my brother's wedding. Guess she have no Scottish blood in her.

I don't want to influence your future relationship with either your brother or future sister-in-law.
A number of years ago my brothers, our children and I had a special weave of our family tartan and had 11 kilts in all made. We also had a few ties made. My twin brother's new wife has never let him wear his new kilt, if fact the last time I saw it a couple of years ago it still had the basting stitches in it. I have seen him wear the tie. They live some distance away, but when we get together, I make sure I am kilted, because I know how much she likes them. Did I wear it to their wedding, no, I wasn't invited (nor was the rest of the family).
All this being said, I would advise keeping the peace at the wedding.