My husband wants to adopt my five year old son. Does the father have to agree if he's not on the birth certificate and hasn't supported his son after the break up? He only saw his son twice in a year and seven days.

Yes the father would have to agree, if he is not listed on birth certificate and there has not been a DNA test to prove his is the father, normally they will require DNA tests to prove he is the father, and he will have to be willing to give up his rights. Once and a while they courts in some states may allow his rights to be taken away, but if he fights it, normally they will not allow him to loose his rights.