I have a friend who lives in Pickerel Wisconsin and his girlfriend told him that in order for his last name to be on the birth certificate (and for there twin daughters on the way) they have to be married. Now i know that not ture where i live, but they do live in the boon docks so i wasn't sure if she was just saying that to get him to marry her or what. I've tried looking it up on line with no success. If some one knows the answer i'd surely appriciate it.
Best way to find out is to contact you local office for Births, Marriages and Deaths.
I am assuming you are from the USA so am not sure what that office would be called (this is a mainly UK site). Over here the father must be present if his name is to be on the birth cert, that is the only requirement, marriage is neither here nor there. I suspect the girlfriend is pulling a fast one.