My sister's kids (2001)

Erik Lund is a professor in child psychology. When his sister and her husband go on vacation, he is left in charge of their five children. He really feels up to it, since he is now going to be able to try out his skills in child psychology. However, reality is something else than theory and children do not always do as they are supposed to, according to his book on child psychology. The children soon fool him into doing as they please when it comes to food and pleasures. However, soon they start to realise that if they can make him serve them hot dogs and hamburgers and let them watch TV as much as they like, they can also make him help them restore their old house, so that they won't have to move, as their parents want to. And, as their uncle is nice enough to help them, they also decide to try and get him a wife.