I feel for you.
it does sound like there is something there, if its for this life, the last or the next wish we know without a shadow of a doubt.
I feel someone from my past was from the last and there is still unfinished business.. but not in this life.
I am with the right one.. the wrong one is the wrong one.. this is the only life I am leading at the moment, not my last or my next.
The fact that you dont feel resentful to his current girlfriend is a very good thing.. something that is having me agree that this could be him.. and that your a grown up leading a fulfilling life not a giggling girt making eyes at prince charming

( oops I just described myself at 20 )
BUT
Do not lead your life as he is.. it is best to lead you life as he isnt and enjoy the union when it happen, than to lead your life waiting for it to happen only to find that this wasn't the life it was meant for.
If hes not a married man you could smile his direction and play it coy with a flippant, "too bad your not available."
lol. only problem is if he is quick to water that seed id be wary of his trustworthy character.lol
If hes married or the relationship is clearly exclusive, just let time happen.
Also I dont believe there is a 1, I honestly believe there could be many 1's depending on our journey.
I believe in soulmates, but not as if there is and only one.