If he is definitely the father then yes, he would have to pay child support, but there are some strange laws about marriage and if your wife should bear a child and is married then the person she is married to is automatically responsible for that child....it's weird I know but I have come across that somewhere in all my findings.
Do the two of you plan on the birth father having visitation? Do the two of you have any children already together? As I am sure you know, this is going to be very emotional for you, especially with the birth father being involved. Is he going to be there for the delivery of his child? Just know that if you are asking for child support, then he (even without supporting financially) has every right to visitation and shared custody to that child. Has the ex boyfriend expressed any interest in wanting to be involved?