We've had family members in a similar situation. DH's uncle didn't see his kids for 10 YEARS after his wife left him.
They only got back in touch in 2008 because DH and I were getting married and invited the kids to come - they are now 19 & 16.
DH's uncle had continued to pay maintenance the whole time, even though she refused to let him see them. She even made the daughter (who was 10 at the time) get on the phone and tell her dad shed never see him again if he didn't leave his girlfriend! He didn't even meet the girlfriend until 2 years after his wife left him!
Thankfully it appears the kids know it is not their dads fault as the son said that he had always planned to go looking for his dad when he was 18 coz he knew "something was wrong".
Some women have a lot to answer for and many, like DH's "aunt" have had to explain themselves to their children.