Thread:Future Beetle/@comment-26534756-20140924224936/@comment-5737527-20140926120404

Oddly enough, Jane's actually right on this one. Twins have to come from the same pregnancy in order to be twins. The closest I can think of for what you're describing is "Irish twins," which is two babies born less than a year apart, but even that doesn't quite fit if they have the same birthday. If you don't want to take our word on it you can look it up.