Peter Pan is about a boy,Peter Pan, who literaly never grows up. Peter befriends three siblings, Wendy, John, and Michael, who leave with Peter to go to Never Land. At Never Land they meet The Lost Boys, Peter's friends, and they all soon become great friends.
I am Number Four is about a high school boy who is really from another planet, but lives in Ohio and goes by the name of John Smith. One day, in the middle of class, John Smith gains his "Legacies" - powers that some people from his planet gain. As he gained his first Legacy, his hands start getting stronger and more resistant to heat.
There aren't many simularities between these two books, but one of them is that Peter Pan and John Smith are both somewhat rebellious. John is rebellious because when somone whose locker is next to John's tells him to stay away from the football quarterback, John doesn't listen and intentionally gets on the quarterback's nerves. Peter Pan is rebellious because when they fly to Never Land, he always flies away from the group and has his own little adventures.