Hopefully this teaches you something about human relationships. It's not black and white. Even though they were separated when it happened, they both obviously still had feelings for one another(which is why they apparently later on got engaged etc). There are 8 billion people in the world, don't go shitting where you eat. There are plenty of people out there, try not to fuck your other relationships in the future because you wanted casual sex with exes of people you care about.

>ur nta, neither is he, separated is separated!

Imagine fucking the ex-boyfriend of the person that raised you right after they split lol
Yep, definely not an asshole!