As the British schoolboys attempt to form their society on the island, they form different relationships with each other based on their personalities and roles. Here are the basic ways each boy relates to the other in these pairs.
Ralph and Jack, though they begin as friends, soon become competitors. Jack is jealous of Ralph from the beginning because he feels he should have been chief. Ralph wants to associate with Jack because he is the other boy who is most respected. However, when Jack begins to lose sight of the goal of being rescued, placing more emphasis on hunting, Ralph becomes more antagonistic toward him. Piggy and Simon have to inform Ralph that Jack hates him. Ralph seems unwilling to see the worst in Jack; even at the very end, he believes Jack will listen to reason and will negotiate with him. Jack will not be satisfied while Ralph exists as a challenge to his power; at the end, he hunts Ralph.
Ralph and Piggy have a one-sided friendship at first, but Ralph eventually begins to appreciate Piggy as an indispensable ally. First Ralph teases Piggy for being overweight and violates Piggy's request to not tell the other boys his nickname. Piggy remains loyal to Ralph despite Ralph spurning him at times. Eventually Ralph realizes that Piggy has the greatest intelligence of anyone on the island, but that Piggy cannot lead. Piggy is therefore the "brains behind the throne," so to speak. Piggy helps Ralph see things he is missing, and he helps keep Ralph focused when he starts forgetting about the signal fire. Ralph does stand up for Piggy, telling Jack it was a "dirty trick" to break his glasses, and eventually going to Castle Rock to try to get Piggy's glasses back. Ralph and Piggy are inseparable teammates from the time Jack leaves the camp.
Although Simon looks up to Ralph and wants to support him and be his friend, Ralph never really appreciates Simon's abilities. Ralph chooses Simon as one of the three explorers of the island, and he takes the advice of Simon and Piggy to continue being chief. However, he doesn't give credibility to Simon when he speaks up at the meetings; he mocks and belittles Simon's contributions and insights as much as the other boys do. He tells Simon to shut up and tells him he's batty. Ultimately, Ralph fails Simon during the feast and unwittingly takes part in his murder. He is plagued by guilt after that, although he and Piggy manage to rationalize away their part in the execution in order to be able to live with themselves.
Simon and Jack do not appreciate each other. Even when they are on the initial exploratory tour of the island together, Jack ignores Simon or belittles him. When Simon calls attention to the candle-bud bush, Jack overrules him by saying it can't be used for anything. When Jack states that the conch isn't needed anymore, an example he uses is that Simon's speeches haven't done any good. For Simon's part, he realizes that Jack would be dangerous as a ruler, so he encourages Ralph to go on being chief. Simon meets his death at the hands of all the boys, but during the dance that Jack has instigated.
Jack and Piggy hate each other. Jack is jealous of Piggy's relationship with Ralph, and he makes fun of Piggy for wearing glasses, being heavy, and having asthma. Jack punches Piggy in the stomach, breaks one lens of his glasses, and later steals his glasses. Eventually, under Jack's regime at Castle Rock, Piggy is murdered. Piggy is afraid of Jack. When Ralph suggests that he, Ralph, should no longer be chief, Piggy tells him that he must go on because Jack hates Piggy and also Ralph, implying that Jack's rule would be dangerous for all of them.
The relationships between the characters are realistic. Because no pair has a flawless relationship, the interpersonal conflicts add to the tension within the novel as the plot unfolds.