If it is not, he is not as good a man as you hope he is. There's enough chaos in this situation for everyone. The kids are already dealing with the divorce of their parents, and they may not be ready to meet Dad's new girlfriend.
After going through a divorce, the last thing anyone wants is a new partner introducing new problems.
Love each other for who you are, not where you've been, but at the same time, be sensitive. Depending on how long he was married, you might find he does things that you find odd or inappropriate. Let him know there are things that may have been okay in his marriage, that are not okay with you.
He will not feel better overnight, so just continue to encourage him through his tough time.
My guy has been separated for the last 2 years but the divorce just became final I believe in June.
As much of a cliché as it sounds, just be there for him, for whatever he needs.