The thing with past exes, you know them. Obviously you have a connection to them whether you want to admit to that or not. There is hardly ever a clean break where one or both partners are completely over the relationship, sex, what ever. So, for me - if my husband was to cheat, I'd almost rather it be with someone he doesn't have a past connection or past relationship with.
I'm very, not sure how to word this, classic? In my dating, relationships, marriage... I want there to be definitive lines, but I want those lines to fall naturally and not be set by me and interpreted just by me, and adhered to just because I made them. I want the guy to be on the same natural page that I am on. Some people say, it isn't cheating until you're at the, "I love you," declaration. If you're sure enough in your own mind to say, "I love you," only then it is time to stop any side relationships and focus just on the one person.
I disagree. I feel that once you establish that a relationship is there then ex-lovers, wandering eyes, dating apps, etc, have to stop. They have to stop and stay stopped.
I made the mistake once of trying to hold on to two people at the same time and I broke someone's heart and I'm glad they found someone else. I just know to stay well away from him for the sake of my sanity and my relationship with my husband.
Also, communication is key. If there are blurred lines between you, they need to become clear. They don't need to become clear by you getting.. "back at him" for being with an ex-lover... to get rid of the jealousy either. I do know that isn't a steady and easy bit of ground to walk on.