It really doesn't sound like you have a problem with the child as much as the relationship to his mother.
He's just a teenager who wants to see his dad. If I have the math right, you and your husband have known each other 32 years, with a total of 27 years married! That's a long time!
Even though your husband made a mistake for 5 years, his son will always be a part of his life. That will never change. I think your husband has proved he loves YOU! I believe you will always have a tinge of jealousy, that is normal.
My advice (although I have never had this problem and shouldn't give advice) is to let him come and find out what kind of a person he is. He is still a part of your husbands life and must have left a great impression on him, you may be pleasantly surprised.
Whatever you decide, I hope you find peace and joy in it.