Divorce finalized after two years but Immigration aware of divorce and withdrawal.

* Did he have to file for I-751 with waiver?
* Or was he able to file as self-petitioner ?
* What would status be of sponsored children ?
* Is having a baby with someone else grounds for permanent green card ?

https://www.askmehelpdesk.com/immigration-law/751-not-signed-266316.html

Since the divorce is final, my advice is close this chapter and move on with your life.