Ugh, I can't stand
Reginald.
Reginald is almost comically stuffy and, at the same time, so slick it's almost slimy.
I don't have a very positive image of
Reginald, obviously, so for sibs I'm afraid I'd pick names that give me a similar vibe:
Araminta (stuffy and spoiled) and
Peregrine (stuffy and weak willed/untrustworthy).
Reginald,
Araminta, and Peregrine...they could be wicked siblings right out of
Masterpiece Theatre, all grasping for the family fortune and stabbing each other in the back between cocktails.