It's been a very long time since I had an EX.  I've been married 22 years now.  Do you know much about those relationships.
I know the term can sometimes have a derogatroy meaning, bringing up unrequited feelings
Yes, I can see how that would happen.  I think many people may have issues due to past relationships.
Ex can mean a few different things besides an former romantic partner.  Such as ex friend or ex co-worker
Ah, I never thought about it that way.  I do have some ex-coworkers.  You really lose touch when you don't work together anymore.
It still is probably most commonly used in reference to an old girlfriend or boyfriend.  Otherwise known as partner or significant other