Hi Bec
I'm not sure if that's possible, or even desirable. I guess it would depend on the circumstances.
I never wanted any of my ex-boyfriends back, but after my divorce I wanted my ex-husband back. It worked for a while, but then the same old problems kept arising. It turned into a cat and mouse game between us, until both of us were exhausted.
When I finally broke it off for good and met my husband, I saw what was missing. My husband loves me as much as I love him. It didn't work with my ex-husband because it was one-sided. He didn't truly love me, and there was NOTHING I could have done to make him love me.
We can't control the emotions and desires of another human being. If we can, it doesn't last for very long.
My ex-husband and I broke up some 20 years ago, and we're both happily married now. We'll never be lovers again, but we've developed a true friendship that benefits us all - including the son we had together.