How does Roman Catholicism deal with the celibacy issue in relation to Peter having a mother-in-law?

Yes, Peter was married. So what? I assume you're hinting around about priestly celibacy.

Catholic priests at one time were free to marry, and we even had married popes. However, the role of the priest is so demanding, that it's better for these priests to be unhindered by a wife and kids. Also, there were the problems of kids thinking they could inherit religious objects or even the role of a priest from their priest dads, and there is the burden of financing a priest's whole family out of donations to the Church.

So priestly celibacy is a practical discipline. It's not dogma. What that means is that it could change at any time.

Were the Church to experience a great deal more vocations to the priesthood, and were laypersons more active in doing the work of the Church, then the priesthood wouldn't be such a demanding role, and there would be more money tithed to pay for the support of the priest and his family. Only then will priests be allowed to marry again. In the meantime, this is ... more.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.