It's wrong to make people dislike each other.
Max is jealous of the friendship that has developed between his girlfriedn and his younger brother.
Max wants his girlfriend to focus on him.
Max sits down and shares his insecurities with his girlfriend and his brother.
Max drops subtle hints that lead to his girlfriend and his brother to distrust each other.
Max is able to gain a better understanding of his girl friend and his brother.
Max ends up damaging his relationship with both parties when his subterfuge is discovered.