This appears to be the sticking point?(if they want)
The main thing is to be sure that they are
not just saying that because they don't want to upset Dad.
I know of one case where Mum had abandoned the kid to his father.
(at the time a "little kid").
She re-appeared during the kid's late teen years, seeking contact.
His Dad made sure to give the boy a genuine choice.
The boy wasn't interested.
Now, as a grown-up, employed, stable, fully functional, young adult, he still isn't.