My thoughts...

If your partner and his best man each have a clan tartan that has meaning to them, they should wear their own colors. As for you, you could take your partner's tartan (I wear my wife's clan's tartan) as you are joining your partner's family. Or you and your best man could look to your own personal histories for a tartan inspiration (Think National Tartans, State Tartans, Service Tartans, etc. etc.) if that doesn't work, what tartan do you like?


Cheers (and congratulations)