The article tries to make the hairsplitting point that "maybe Peter had a mother-in-law because he was married at one time, but his wife died" as a way of getting around the obvious fact that Peter was, in fact, married. This fails on two points:
1) Paul quite clearly states that Peter and other apostles were "leading about wives" (i.e. were married) in I Corinthians 9:5, and indeed, he makes the point that he, himself, was perfectly within his rights to do the same.
2) In that culture, when a woman's husband died, she returned to her own kinship group. If Peter's wife had died before his calling from Jesus, his former mother-in-law would have returned to her own ancestral family to be cared for by them, not Peter.
You are both neglecting an important distinction. Peter was already married when Jesus called him. Some of the Eastern Catholic and Orthodox Churches follow this approach and allow married men to become priests. However, our Lord was celibate and called it a gift from God (Matt. 19:11-12). Paul also acknowledges that celibacy is a gift from God and wishes that all were celibate like he is. (1 Cor. 7:7).
Celibacy is a practice in the Catholic and Orthodox Churches. It is not dogma.