That doesn't mean that you two have to split up...

More like your step sister.

You don't actually break up with her, you keep seeing her behind their backs. If they're going to act like a couple of arbitrary and controlling cunts, then lying is a perfectly acceptable response.

This. Or you just ignore them and stand up for yourselves. Just because they're your parents doesn't mean you have to accept everything they demand of you.

You’ll have to stop representing yourself as a couple publicly, and just conduct hot step-sibling incest in secret.

Of course, your kids are going to come out ret..., um, developmentally exceptional.

...thats only if the people are blood related... fucking blood related.

I was being facetious. I know that!

Sister-in-law? Wouldn't she be her step daughter? Cause it's your mom and your ex girlfriends mom?

You are right!

Given the quality of editing for spelling and grammar here, are you surprised that genealogical blunders sneak through?

Technically she would be the moms sister in law and she would be his sister.
Either way this is really messed up for the 2 of them

That sucks

Tell them if the two of you can’t date each other, they can’t date each other either

she would be your step sister not your sister in law. and since you 2 aren't related I don't see what the problem is.

If you were dating first then the moms should be the ones to break up.
This is also really creepy how much time did they spend together that they fell in love.

If your moms marry each other, she wouldn't be your sister in law. She'd be your step sister. Your sister in law would be if one of you married the other's sibling.