Well, we only have one so far, but for our next I'm trying to go for the same... vibe? Nothing as matchy as alliteration, rhyming or whatever, but names of a similar heritage (ie ours: Anglo-Saxon/Irish/Scottish), and that just sound good together. I think it'd sound odd to have kids called, say, Tiffanee-Krystal and Gertrude... or James, John and Tyrone. You know?
F'rinstance, DD is Rowan. If this next babe is a boy I really like Robin, but I think Rowan and Robin sounds a bit funny together. Too similar. So that's out.
My parents did all Bible names for us, which is semi-noticeable because there are six of us and we're all girls. Funnily enough, the youngest is Abigail (Abby), and a lot of people don't know that's a Bible name. So we got a lot of comments about how my parents "broke the mold" or "ran out" with her.
She married King David, but I guess she's not as well-known as Sarah or Ruth!