Rainman’s plot heavily focused on the theme of hypocrisy throughout the movie. The father of main character Charlie Babbitt, passed away. Charlie expected his dad’s estate and fortune to go to him. He was surprised to find out that the fortune actually went to an autistic brother he didn’t know he had. He then tries to become the legal guardian of his brother and claims that it is because he wants to spend time with him when he just wants the fortune. Throughout the movie he slowly becomes closer to his brother and begins to do stuff with him not to get the fortune but because he is truly enjoying spending time with his brother. What started out as a hypocritical relationship with his brother gradually evolved into a feeling of caring for a newly discovered family member.
The Best of Rain Man
this video shows some scenes of Rainman that show that charlie isn't taking care of him because he's his brother but because he wants the money.