Beatrice and Bennett. Thumbs up
Beatrix and Benton. Thumbs up
Bianca and Benedict. Thumbs up
Belinda and Bennick. Thumbs up
Bernice and Benjamin. Thumps up
Beatrice and Benedict---while lovely---I just don't know. Most people won't make the connection, so it's not like naming your kids Romeo and Juliet, but it is a tad bit funny. I'd ask your family and friends and see what they think. I wouldn't use the names for twins, but for siblings especially if there's another sibling between them, I think it would be okay.
I like them both and think they go well together. I don't think that most people know Shakespeare enough to be concerned about the link. You could also move these 2 names to the middle though.
Oh, I don't know. I adore the name Benedict, and it does sound great with Beatrice.
I do think Benedick and Beatrice would be a bit much. Too matchy, though not precisely creepy.
As long as you or the kid can believably give a puzzled look and say, "No of course not, that was Beatrice and Benedick, not Benedict" when someone brings it up you might be okay. As if it's just odd they'd think that two similar names are the same.
Not a Shakespeare keener by any stretch but these names immediately made me think of the couple from much ado about nothing. i think its odd for siblings, yeah,
I immediately think of the couple - but the names do sound lovely together!