Ugh. Really. Well, if I had to I'd go with
Michelle, because most of the time it doesn't have a nickname, in my experience anyway, and I think that most Nicoles go by
Nicky or
Nikki or some form of that, and I don't like it.
Michelle Vivien, why not? Her brother and sister would be
Victoria and
William, because I don't care about sibsets "going together".