The friendship between brothers Conrad and Jeremiah Fisher starts off as strong and affectionate. They both dearly loved their mother Susannah, but shared different opinions regarding their father Adam (or Mr. Fisher, as he is often referred to in the novel). Since Adam frequently cheated on Susannah, emotionally mistreated them and even left them when her cancer returned, Conrad personally hated his father. However, Jeremiah wished to see the good in him even though he harbored resentment for Conrad being favored over him. Despite this, the two brothers still loved each other and looked out for one another.
However, their bond is challenged when both boys fall for their childhood friend and best friend's younger sister, Isabel "Belly" Conklin. It is well known by their whole family that she liked Conrad since childhood, but when Belly is left questioning her personal feelings for Jeremiah, the three soon find themselves in an intense love triangle. Conrad and Jeremiah soon finds themselves in a rivalry for her affection, which challenges their strong bond as brothers.
The Summer I Turned Pretty
Both Conrad and Jeremiah are waiting outside the beach house for the Conklin family to arrive like every summer. However, when they see Belly, they both instantly see her as "a girl" and no longer as a little sister figure as every summer before. This results in both boys falling for her.
They also are both aware that their mother Susannah has fallen ill again with her cancer returning, but pretend that they don't know. While Jeremiah wishes to make this the best summer for their mother and tries to act normal, Conrad instead begins drinking, smoking, hooking up with girls and staying locked in his room. Jeremiah eventually confesses his feelings to Belly, hoping to start a relationship with her. When Belly admits to still liking Conrad, Jeremiah is left heartbroken that Conrad is always the one for her.
Conrad and Jeremiah reach a fight over how he has made their mother worry so much. This leads to Belly finding out about Susannah and being grief stricken. She goes to Jeremiah's room late that night and the two comfort each other, with Jeremiah saying how much he hates Conrad for what he has emotionally done to their mother. Belly continues to comfort him and they soon fall asleep side by side.
However, upon the realization everyone knows, Susannah calls for a family dinner and makes a declaration of her putting up one last fight. She then says she wants to stay with her family until the end of it, resulting in everyone making amends with each other. Jeremiah even steps aside to let Conrad have Belly, even though seeing the two together bothers him.
It's Not Summer Without You
The two brothers still have a good relationship, but still have their differences about how to go about making the best of their mother's remaining time with them. Conrad continues to lock his emotions up and be a jerk to everyone, infuriating Jeremiah since he wants their mother's remaining days to be happy. When Susannah dies, their bond meets even more strain. Jeremiah also grows sick of seeing Conrad emotionally mistreat Belly and his feelings have grown very strong for her.
Later on, when Conrad disappears all of a sudden, Jeremiah calls Belly to help find him. When they find him at the beach house, they try to convince him to return to university in order to take his final exams. When they find out about their father's intent to sell the beach house, they all band together to keep the remaining and most important item of Susannah. After convincing him to let them keep the house on the condition that he pass his exams, the three "summer kids" help prep Conrad for the exams.
At first, everything goes smoothly with it seeming like it was going to end on a happy note for them. Conrad successfully passes all of his tests, ensuring that they get to keep the beach house after all. However, when waiting for Conrad to return from his final exam in the car, things take a turn for the worst when Jeremiah is unable to deny his feelings for Belly any longer. He abruptly kisses her, who returns it, and he admits he still loves her. The two end up briefly making out, only to be walked in on by a near furious Conrad.
Following this, things between the three become tense and awkward. After being forced to stay put in a motel due to heavy rain, Conrad tells Jeremiah he can take his chance with Belly and claims to no longer love her. After this, things smooth out with them again.
We'll Always Have Summer
In the final novel, two years have passed since the previous novel. Conrad joins everyone for the dinner celebration of Susannah, albeit late. There appears to be some awkward tension from Jeremiah towards Conrad, however, which confuses Belly. At the dinner, Conrad, like everyone else, is shocked to hear about Jeremiah's engagement to Belly given how young they still are. He facially, however, shows no emotion and simply ignores Belly and Jeremiah as he simply leaves.
When Belly ends up staying at Cousins Beach due to her mother kicking her out of the house, Jeremiah is shown to be nervous about the arrangement given how Conrad is also staying there. While they still have a mostly good relationship, it appears that Jeremiah is jealous of Conrad and Belly's close friendship together. This is shown in moments such as when he kisses her in front of Conrad while looking right at him and having clear tension the first time the three were together. Conrad attempts to persuade Jeremiah to hold off on marrying Belly at least until college graduation, only to be met with anger from Jeremiah.
Conrad (through his narration chapters) is soon revealed to be jealous of Belly's engagement to Jeremiah, still more than in love with her since the last time they saw each other. He is revealed to have lied to Jeremiah in the motel years before when claiming to no longer love Belly and giving him a chance to have her instead. He had only done so because he was unable to see himself hurt Belly again and trusted Jeremiah to take good care of her. However, seeing the two together greatly pains him and despite his promise made to Susannah on her deathbed to take good care of Jeremiah, he is finding it increasingly harder to resist his feelings for Belly.
Conrad also finds himself surprised by his brother's new lifestyle - he is annoyed with the immaturity of Jeremiah's friends as well as his own new and selfish personality. Upon finding out about Jeremiah cheating on Belly while at his bachelor party, Conrad is left outraged and almost beats up Jeremiah. However, Jeremiah is locked in the bathroom (throwing up after getting drunk) and Conrad instead leaves to calm down.
When Conrad is later found by Belly along the beach after the party had ended, he doesn't hesitate to tell her about what he heard. Shocked and disgusted to hear about Belly already knowing about it and still willing to marry Jeremiah anyway, this leads to an argument between the two before she leaves. Unable to deny his feelings any longer, Conrad confesses his love for Belly. Despite his heart felt confession, she rejects him.
Belly later tells Jeremiah what Conrad told her, leading him to want to beat up his brother. When Belly attempts to calm him down, Jeremiah accuses her of still loving Conrad and only marrying him to erase her feelings for Conrad. Despite Belly insisting otherwise, he takes off before their wedding day. Conrad soon finds him at their mother's garden and attempts to convince him to return to Belly, but he refuses. Jeremiah brings up Belly and they begin to fight over her, with Jeremiah insisting he never went behind Conrad's back when it came to getting Belly. Conrad brings up how it didn't look that way when he walked in on him kissing her years prior and how he trusted him to take care of Belly qhwn giving him his chance to be with her. But despite that trust, he cheated on her and remarks if he even actually loves her. At this, Jeremiah ends up punching Conrad in the face two times before they continue arguing over who loved Belly more and deserved her. Jeremiah brings up all the times Conrad hurt Belly and treated her like garbage, but he still refuses to admit that he loves her. Conrad then finally admits his genuine love for Belly and how she is the only girl he can ever love and truly be with.
He then hands Jeremiah one of the final letters left from Susannah, meant to be read on their wedding days. Jeremiah is left in tears after reading it, before disowning Conrad as his brother and declaring he is out of his life. He then hands the letter to him, revealing it to have actually been the letter meant for him, not Jeremiah. Conrad then begins to cry.
- Conrad is a year and a half older than Jeremiah.
- Both have been narrators in one novel of the trilogy. Jeremiah narrated a few chapters in It's Not Summer Without You and Conrad did so in We'll Always Have Summer.
- They were both part of their school football team. However, Conrad quit the sport while Jeremiah went on to excel in it.
- They each have/had feelings for Belly and dated her and are the only serious relationships she has ever had. They also have both been engaged to her at some point in their lives. However, Conrad was the one to have eventually married her whereas Jeremiah's relationship with her crashed and burned.
- It was because of their rivalry for Belly that resulted in the ultimate - albeit brief - demise of their friendship together. The two did not talk to each other for at least a year before making up again.
- They are both polar opposites of each other. Jeremiah is an extrovert and is highly expressive of his feelings and is outgoing, whereas Conrad is an introvert. He is well known for always hiding his emotions and rarely ever expressing what he is truly feeling.
- They both fell for Belly after noticing her as a girl, no longer a little sister figure, during The Summer I Turned Pretty and possibly even at the same moment.
- Jeremiah was very open in his affection for their mother Susannah, even doing things such as holding her hand when he was too old for it. Conrad on the other hand, had a very hard time expressing his feelings for his mother, even during her time with cancer.
- Conrad had been their father's "favorite", always taking him out for trips and favoring him over Jeremiah. Conrad had taken note of this, leading him to stick up for his brother at times, and it was part of the reason why he distanced himself from their father as emotionally far as possible.
- They are both very popular with girls; Conrad for his quiet, alluring personality and handsome appearance and Jeremiah also for his good looks as well as open and funny personality.
- They have each once stepped aside to let the other get together with Belly despite their own feelings for her. After both falling for Belly in The Summer I Turned Pretty, they each wanted to start a relationship with her by the end of the novel. However, Jeremiah allowed Conrad to have his chance with her first, even though he had grown to genuinely like her. By the ending of the second novel, Conrad reluctantly stepped aside to let Jeremiah have a chance with her despite his own love for her. Both times, they reached a point where they had grown sick of seeing the other emotionally mistreat Belly and ended up confessing their feelings for her with hopes of getting her back from the other.
- Some readers were left upset at the ending of the two's relationship in the finale novel. This is due to how the book did not specify if their relationship ever properly healed. However, in bonus content in the paperback edition of We'll Always Have Summer, the readers got to see the early letters Conrad wrote for Belly during her time in Spain. In one letter, Conrad revealed that he eventually met back up with Jeremiah during a dinner at Laurel's house. Despite things initially being awkward between them, the two began talking again. Conrad tells Belly that he believes Jeremiah "doesn't hate [him] anymore". Given that Jeremiah is also seen at Conrad and Belly's wedding in the epilogue of the final book, it is left to be assumed their relationship healed.
- When Conrad and Jeremiah were kids, Jeremiah hated his curly hair. Conrad had convinced him that eating the crust on sandwiches caused his hair to curl, so Jeremiah had stopped eating crust until realizing the lie.