Jehan Frollo betrays his adopted brother, Quasimodo, when Quasimodo is being questioned in the court, he doesn't tell a soul that Quasimodo is deaf and can't answer any of the judge's questions, this leads to Quasimodo being beaten at the pillory for being deaf, which is no crime at all.
Jehan also betrays Claude Frollo, the brother who loves Jehan and spends his life taking care of the boy. Jehan never takes to heart any of the things Claude Frollo tries to teach him, but instead only uses Claude Frollo to get money, which he then uses to visit taverns where he buys drinks and soon after finds an accommodating wench. So, in the end, we can conclude that Jehan was an utter bad word, and was possibly the world's most selfish person, considering all he ever did was look after his own well being.
Not only is Claude Frollo the betrayed but the man also does his share of playing the role of betrayer. He completely turns his back on God and abandons his faith to lust and obsess over La Esmeralda. Quasimodo is also affected by Claude Frollo's betrayal, Quasimodo suffers at the pillory while Claude Frollo goes by, ignoring the fact that his adopted son is being beaten right in front of him.
Phoebus de Chateaupers betrayed La Esmeralda because he acted as if he returned her love, when he didn't really, he lied to her and made her think he loved her when all he wanted was her body. Phoebus had his share of other women at taverns and such, in this way, and in the fact that he pursued La Esmeralda, he betrayed his fiancée, Fleur-de-Lys. He made Fleur-de-Lys think she was the only woman in his life, when he was in actuality, not true to her.