It is different for kids because we *are* responsible for them, unlike other people. You aren't so much helping dad out, you are helping the little boy out, who really is just a child and can not always figure things out on his own.
If my xah was supposed to do something for his mother and did not follow through on that - I went and did it. If I had to do that over again, I would not do it. His mother was an adult though. She *can* figure things out on her own. I was not helping her, I was helping my xah.
I've not had to manage a step child relationship. My hats off to all step parents out there!!