It's good to be there for your step-kids.
Charlie marries Betty who moves into his house with her two kids from a previous marriage.
Charlie wants to decide how to treat his new step-kids.
Charlie tells his step-kids that even though they aren't his biological children, he will always help them out just like a father.
Charlie tells his step-kids that they aren't his, so they need to stay out of his way.
His step-kids become very attached to Charlie and think of him as a real dad.
His step-kids resent Charlie and always look for ways to undermine his marriage with their mother.