Hi TearsInHvn
Yes, a difficult one.
It may be that he seems great just now, because you are unhappy in your marriage ~ the grass is always greener on the other side ~ or it might be that he was, and still is, your soul mate and that you should end your unsuccessful marriage and start afresh with him.
But, really, how well do you know him?
You knew him when you were kids, but, presumably, you haven't been involved with each other in the meantime, when you were bringing up children?
Do you know why he is unhappy with his wife?
Do you know if he is a good husband and father?
Do you know that he would make a good partner to you?
Maybe the same things would go wrong again ~ who can say?
You say that you are in an unhappy situation.
Have you done anything about that?
Have you tried to heal your marriage?
Or, if it is beyond salvation, have you discussed separation or divorce?
Would you be considering leaving your husband, if this man had not come into your life?
Your children are grown up, but his daughter is only 13.
Are he and his wife considering divorce?
Would he be willing to leave his family ~ including this young girl ~ for you?
Is this real, or is it just a dream romance?
You need to give this whole situation a lot of thought.
For each of you there are at least two issues ~
~ Do you want to leave your partner?
~ Do you want to start a new relationship with each other?
At your age, you have time to start over and have a great life together ~ but it won't be without complications, because you both already have families.
I don't know how you can tell whether this would be a forever thing for him. How would you even know that it could be a forever thing for you?
Maybe he is reticent about phoning you, because both you and he are already married to other people and have families. I think a lot of people would be wary in those circumstances.
Would both of your spouses agree that the marriages were 'unhappy'?
Perhaps you should decide, first, whether or not your marriage is over, and whether you could go it alone, if this new 'relationship' doesn't work out.
Good luck