Sadly there isn''t anything you can do, and its really really hard. You cannot force a parent to have contact when they clearly don''t want to. Most absent parents would do anything to see their kids and be a major part of their lives, but some don''t. I don''t get it, you don''t get it, and to be honest I don''t want to get it, because it must be a very dark place to be.
All you can do is be the best parent you can. Try and answer their questions as honestly as you can (age appropriate), but don''t build their hopes up either. One day, if things don''t improve, they will probably turn their backs on him, which is sad, but par for the course when no effort is made. We are seeing what it does to a kid ourselves, with mum being the absent parent. My 13 yr old SD has lived with us now for 8 months, and in that time her mum has seen her 6 times for a total of 18 hours. SD, despite being encouraged, didn''t send her mum a card on Mothers Day. Her choice. Mum was livid with her and had a go on the phone. SD told her she didn''t deserve one because she doesn''t behave like a parent. Fair enough really. Their relationship is in tatters, and she only has herself to blame.
You just have to be there for your babies, like all good parents are.