You know what... I'm reading a bunch of this garbage in this thread and I am happy to not have a lot of you for my friends. Really. This dude obviously thinks enough of RTDB to ask him to be his best man. Enough said. If I'm RTDB, I reply with, "I'm there, wow, thanks" and that's the end of conversation.
I have two brothers and they will no doubt be my best men someday. If I didn't have any brothers and had to rely upon my best friend to fill in, I would fully expect him to do as much, because if the roles were reversed, he knows that I would be there for him.
Take the vacation with the wife the following year.