I know lots of folks named Nancy. Three are pretty good friends. So we all know that it's not uncommon for people to share a name. (Full disclosure: I like that there aren't many Aprils.) But don't ever give your characters the same name. It just confuses the heck out of your reader.
In fact, don't give main characters the same first initial. When I read Hearts and Bones , I got all the male characters confused: Jeremy, James, John, Jake, Jebediah, whatever - there were three or four main guys whose names started with J. I didn't realize until I was halfway through the book that in my head I had combined two characters into one.