How could Peter be the first pope if he had a wife?

Answer 1

Peter was married before he became an apostle. Also, the prohibition of a married clergy did not come about for over 1000 years.
The celebacy rule for clergy was not put into place until long after Saint Peter was the pope.

Answer 2

It doesn't appear that St. Peter was married when he started to follow Christ, it only appears that he had been married, there is a pretty good chance that he was a widower when Our Blessed Lord called him. His mother-in-law

is mentioned in the Scriptures so we know that he had been married, but not that he was at that time.

Answer 3

The celibacy rule did not come into play until many years after Peter died and several of the early popes were married. There is nothing in scripture that names Peter's wife. However, some traditions and apocryphal writings mention that Peter's wife accompanied him on some of his missionary travels and died as a martyr before Peter's own execution.