dmr wrote:

I have nothing to do with that guy, his ex or his actual girlfriend.

Now let me understand. Let's say you were that guy: You would be ready
to keep your kids away from their mother simply not to pay full child
support? Do you care about how the child feels about that?

And yet somehow you feel justified in maligning his motives. Boggles
the mind. How do you know that he is doing that "simply not to pay full
child support"? And since when did child support only encompass the
money that you pay out of hand. Doesn't the father pay for rent and
utilities? Isn't the child receiving the benefits of that? The father
is simply choosing how he meets his particular obligation, which is
within his rights.
But turn this around: how do you know that the mother isn't merely
wanting to keep the children so she can get more child support money?
Just as logical as what you've suggested.