If a woman is married and has an affair that results in a child, I realize that by law the husband is presumed to be the father unless a paternity test proves otherwise. However, can the biological father come in a year or two down the road and insist on a paternity test, visitation, etc.

I realize that if both the mother and father agree, the biological father can relinquish the parental rights; however, it seems that in this case a paternity test is required. If so, how does this impact the husband? Would the husband, who would have already signed the birth certificate, etc. be required to adopt the child after the parental rights were terminated?

Yes if you and your husband is on the birth certificate and nither one of you want the other person in the picture you don't have to agree to get a paternity done that way your husband still has his right's and the other guy is SOB... TRUST me it will SAVE you lot's of money in the long run...

Yes, the bio dad can come in down the road and request a paternity and then custody/visitation. That would leave the husband as the step father.

The bio dad can, after establishing paternity, relinquish his parental rights if the husband is going to adopt the child. Paternity can be established at this point by a DNA or mutually signing a court order agreeing to paternity.

Even though the husband signed the birth certificate he would still be required to adopt the child to become the legal father. (If the bio dad establishes his paternity, that is. Because right now the husband is currently considered the "legal" father.

It depends on where you live... Some states allow that action-other-does not allow it.If I have info where you live I will give you a full and correct answer.

Some states allow what action GV?

However, can the biological father come in a year or two down the road and insist on a paternity test, visitation and etc...
That kind of action... Some states allow BF to bring paternity action,other-do not allow it if there is an intact family and presumed father.

Any obscure?