Many parents give their twins matching names. In fact, maybe most do: on the 2005 Popular Names for Twins list, the majority of pairings “match” somehow — starting with Jacob and Joshua (pair #1), ending with Tanner and Tyler (#106).
I think matching names can be cute, but I’m not a big fan of names that match very closely. For instance, there’s only a one-letter difference between Taylor and Tyler (#6) and Jayden and Jaylen (#97). Also, sets like Brian and Brianna (#91) and Jada and Jaden (#96) are basically just male and female versions of the same thing.
I personally prefer names that match on a more subtle level. For instance, I think Olivia and Sophia (#45) go well together because they’re distinct, yet still share that “-ia” ending. I also like Nicholas and Zachary (#53) because they’re both dactylic and have that hard “ch” in the same spot.
How about you — how “matchy” would you go if you had twins? (Would the twins’ gender affect your decision?)
UPDATE, 2013: Give Your Twins Unique Names is a more recent post on this topic.