I think sibling names should sound sensible together (I wouldn't name siblings Susan and Cleopatra, for example), but I don't think they should match. They're individials, and should be named as such. That goes for twins too. I am strongly against giving twins matching names, because it just perpetuates the stereotype that twins are carbon copies of each other. Someone I know named her twins Jasmine and Yasmine. Her explaination was, "I thought it would be cute because, you know, they're twins!" Yes. Yes they are. I don't think they're going to forget that fact. They really don't need names that scream it.
Personally, if I had a sibling with a name that matched mine, I would feel rather cheated because I would feel as though my parents had chosen my name just because it matched, not because they loved it.
Sometimes I just feel like smacking people with the dictionary, just to see if they absorb any intelligence through osmosis.
-My friend Emma