Also - they may not be identical. I have fraternal twin daughters, who appeared on the ultrasound to be sharing a single placenta (as about two-thirds of identical twins do - the other third have separate placentas just like fraternal twins: it has to do with the stage at which the egg divided). The ultrasound technician said the placenta was so big she was pretty sure it was two that had implanted side by side and looked like one, and it turned out she was right. Though I have a lab report from after they were born that says it was a single placenta (I don't think they looked at it very hard). Anyway, my daughters have different coloring and indeed different blood types.

We gave our daughters first and middle names that were similar in terms of being the same general type of name - about the same length, the same degree of fanciness/plain-ness, and so on - but not rhyming, nor the same initial. (And we would have done the same had they been identical after all.) I'm trying to think of a good example that isn't actually their names - say, Rebecca Anne and Caroline Jane. So (in this example) both have the same number of syllables, but the accents are on different syllables, and one first name ends with a vowel and one doesn't, and so on. Inevitably people sometimes forgot which name went with which girl, but that happens with lots of siblings.