[Dr. Sivana]

We know Peter was married (how do you have a MIL if you’re not married)

I don't have a lot to add to the other thoughtful responses to your question. However, there is no evidence that's Peter's wife was even alive at the time of Our Lord's Ministry. It is odd that a mother-in-law would be mentioned, but neither wife nor children. Widowers, of course, can be priests without impediment.

[AnAmericanMother]

It is odd that a mother-in-law would be mentioned, but neither wife nor children.

And also, when Christ cured Peter's mother in law of a fever, she rose up and waited on them.

If Peter's wife had been alive at the time, it would have been her place to wait on Christ and the disciples, not his mother in law. So it seems probably that he was a widower.