Quickchange, obviously I don't know your new man but I would want to fin out how the distance developed and why. He is the parent here and it is up to him to maintain a relationship with his children, no matter how old they are now.
My H left me for OW almost a year ago now and his relationship with our DC, both at University, aged 18 and 20, has definitely suffered.
He has immersed himself totally in his new relationship and even though he lives just 20 mins away from them, when they are home, he will only see them maybe once every two or three weeks. And then just for an hour. They have been home with me since the end of May (long holidays).
Now part of this is the DC choice, they have no wish to meet OW or stay at their dad's/OW home. But he is an affluent man who can afford to take them away or do things with them. He just doesn't.
The C also say that Dad is boring he doesn't talk about anything interesting or do fun things with them. I feel this is because they have grown to be young adults and he no longer any idea how to relate to them, particularly as they are girls.
My DC are very upset about this and will not tell him as they don't want to make the situation worse. It has got to the point when on some occasions they do not answer his calls.
Sad for them all, but as I say he is the parent and the onus should be on him to rectify the situation.
Your new man may well be a good one, but these things do happen, so for your own peace of mind you should ask.