Thurston I had exactly that problem. A boy who's mother married six weeks after he was born, but never put the father on the birth certificate, and when he married nothing of his father on his marriage certifcate either. Finally, after years being clueless, I found this boy's christening entry in the church records, and it turned out that his father was the man his mother had married after all.
Find his baptism if you can, there's a good chance they wouldn't lie to the church.