Marriage has NEVER been forbidden and DIVORCE is NOT the unforgivable sin.
Celibacy of the Catholic priesthood is an administrative policy, it is not based in Scripture nor does it have to be. Democracy and air travel are not in Scripture either.
"and DIVORCE is NOT the unforgivable sin."
Whoever divorces his wife and marries another, commits adultery against her; and if she divorces her husband and marries another, she commits adultery"
- Mark 10:11-12
We know that he had been married, but we know that only because his mother-in-law is mentioned. His wife is never mentioned. We have to infer her existence from the mention o his mother-in-law. It’s a proper inference.
But since he’s never portrayed as “actively” married and his wife is not mentioned, no children are ever mentioned: who knows whether she was even living at the time he left his nets to follow Jesus or, if she was living(possible) whether they had marital relations after that. Telling the world whether you and your wife are doing the deed regularly or not is not something most of us are going to do. It’s not exactly the sort of thing you’d expect to make its way into Scripture.
Nothing in Scripture precludes the possibility that Peter and his wife practiced continence after he was chosen to be the head of the Twelve, if she was even still living at that point.