I just don't understand why you can't see it for what it is. He's breaking Izzy's heart? You're no better for severing a bond between sisters.
As I've told you since the beginning of your affair karma would catch back up to you. You had the opportunity to let him move forward happily. We were all moving forward then you dragged him back.
I know it took me forever to realize it was done but I did. All I've ever wanted was his happiness. He has found that and you should be mature enough to respect that and move on.
Were you really naive enough to believe just because you were having a son it would drag him back to you?
You never really knew him. He gave his true self to B. He just got lost along the way. I've finally found acceptance because my best friend has found her happiness.
With every ending comes a new beginning. Life is what you make it. If you want happiness then strive for it.