I have a relative called Josiah, but when two of his children marry he is referred to as Joseph.
Another relative has a very wrong father's name on his marriage certificate, but with a bit of digging, I realised it had been mixed up with his wife's father's name. Their occupations were the wrong way round, too.
We should bear in mind that the information recorded on the certificate is only as accurate as the person supplying it. Someone might not know their father's real first name, maybe if both parents had died some years previously, or if the father was commonly known by their middle name.