You know, I have mixed feelings too. I know you know that his parents have no obligation to pay his child support. But I get the sting of them not wanting to help HIS kids but they turn around and buy him a house.
That being said, from experience, you're likely better off that they didn't help out. "Help" like that often comes at a price. My kids' father was a man child and came from a decently well-off family. When we split, his mother and grandmother "played nice," offering finanical help to me for the kids. The worst mistake I made was to accept. They saw that "help" as a means of control and suddenly thought they had some say in my life and how I rasied my kids. Long story short, after a few months, I told them to shove their money up their asses. We struggled for a while, but you know what, I'd rather struggle and know I did it on my own and own noone anything than be governed by someone else. Just my perspective. :)