Yep, "alibi" talk.

Maybe your "sex addiction" a "heritage" from your parents. Sorry, I do not want to hurt you.

With all the respect to you, I wouldn't use the word WEIRD to describe your parents sexual habbits. I wpuld prefer the word DIFFERENT.
My parents are similar to yours: they are swingers and have many different lovers. Their lives, their choice.

I'd only call it "cheating" if they agreed to be monogamous and are not sticking to that, going behind each others backs.

Most branches of Christianity teach that monogamy is the one true way so at a wedding the bride and groom each promises: "To love and to cherish....forsaking all others, until death us do part." If someone stands there and makes that promise then I think they do their best to keep it, but that view isn't held by everyone. There was a branch of Christianity that had an argument about polyamory in the past and some non-Christian religions support it.

Then increasingly, some people don't have a religion as such and can choose their own way. That can be being in love, living together as a couple including having children, but feeling free to have sex with other people if they find it exciting. I can also mean rejecting the "until death us part" in favour of "until we're both bored with it" or "until the children have grown up" etc.

You have to work out what you value. Whatever you do, try to be honest with both yourself and others.

This kinda stuff probably happens more than we know.

according to my aunt, the bomers and their parents were far worse