- „It is worse to be incapable of loving than to not be loved”
Jack and his younger sister, Andie, arrive in Capeside in 1998 beginning their sophmore year at Capeside High School. The two of them, unbeknownst to the gang at first, look after their mentally ill mother, Andrea, while their Dad has left the family.
Jack is a calm, introvert, kind presence at the beginning of the series, slowly opening up to everyone and, after coming to terms with being gay, he is seen as more extrovert and at ease with friends and meeting new people, exploring his love life and identity throughout the series.
While Jack is incredibly intelligent, possessing academic prowess in league with Andie and Joey, he is also acutely discerning with regards to human interrelations. This ability, which makes him a great friend to the gang, also in later seasons display his sense of notoriety, which sometimes needs to be balanced. Most often counters to this tendency come from Grams, Jen and Joey.
When Jack first arrives in Capeside, he is described by Andie as 'shy, but great and really smart once you get to know him'. Jack starts working at The Ice House with Joey and Bessie, both of whom view him as a bit of a klutz, Bessie referring to him as 'chore boy'. As Jack and Joey get to know each other better and Jack kisses her, they begin a relationship after Joey breaks up with Dawson. Joey mentions at one point that she feels like Jack is somewhat withdrawn from her in their relationship. His shy and awkward ways are revealed to be from suppressing his nature and coming to terms with being gay.
Although it is a harrowing experience for Jack as his father in unsupportive and Jack and Andie throw him out of their house, Jack seems overcome with relief that he can finally live his true life and no longer hide who he is. During this time Joey is still a support to him, and Pacey as well, who befriended Jack through his romance with Andie. Jack's first encounter with a guy who is interested in him fills him with terror as he does not feel ready at all to date. Jack befriends Jen and she briefly moves into Jack's house with him, after Andie leaves to receive medical attention, and the two end up moving in with Grams.
Jack's relationships with Jen and Grams changes his life. From Season 3 onwards, he has a home and steady core of support in his life, his friendship with Jen akin to that of Dawson and Joey – soulmates who connect deeply. Although Jack and his father mend their relationship and start anew, Andie leaves for Italy and sees his family less frequently for the remainder of the series.
Jack meets Tobey in Season 4, who becomes his first boyfriend. As Jack leaves Capeside for college, he changes quite a lot, wanting to leave behind the 'persona' or label he feels he acquired there, of either 'Andie's brother', 'Joey's boyfriend' or 'the gay kid'. This results in him dumping Tobey and slacking off at college, until he finds himself utterly unrecognizable. Although Jack rectifies his academic career, as that is something he wishes to do at the end of Season 5, he is portrayed in relationships as someone who doesn't really want to be in a relationship, but he still has one with David (which does not end well for that exact reason).
While Jack seemed certain of his interest in art, and later more so himself overall as he came to terms with his sexual orientation, he later seems unsure of what he wants in his romantic relationships and also less close-knit with the Capeside gang, save for Jen with whom he manages to reconnect in late Season 5 and the final season.
Andie practically introduces Jack to the series, and to everyone when they arrive at Capeside, almost being a sort of spokesperson for Jack, who she refers to as shy. The two have a very close relationship, talking more like friends than siblings at times and end up sharing a friend group as well. Whilst Jack is more reclusive emotionally and socially in the beginning, he begins to open up and when he comes out to his father, Andie stands by her brother and throws their father out of the house for being so unsupportive. Once Jack starts coming to terms with all the changes he's made, he is able to support his sister when Andie suffers increasingly depressive disease and has a breakdown.
Jack and Jen first meet on a blind date and become close friends when Jen is kicked out of Grams' house and Jack offers that she move in with him. Later the roles revert when Jack moves in with Jen and Grams. They bond over being fellow outsiders, each in their own ways, although Jen feels more like this personally, whereas Jack is a popular guy who experiences discrimination because of his sexuality. Their friendship is one of the strongest on the show and when Jen sadly dies in 2008, Jack adopts her baby daughter Amy.
Jack and Pacey become relatively good friends mainly when Pacey is dating Jack's younger sister, Andie. However, Pacey comes to be protective of Jack when Jack is forced to read out his personal poem in class by their bullying teacher. Pacey wants to go after Jack to comfort him, but is stopped by the teacher, with whom Pacey has a heated argument culminating in Pacey spitting in the teacher's face. Jack and Pacey remain friends and in college they move in with Emma Jones, becoming flat mates.
Joey and Jack first meet in Crossroads, during a fight between Dawson and Joey. Jack proceeds to continually surprised Joey with his keen discerning of human nature, though she also thinks of him as clumsy – this perception is later rectified. As they become friends, Jack finds himself drawn to Joey and kisses her. She kisses him back and eventually breaks up with Dawson, shortly after starting to date Jack. The two have a relationship for a while, until Jack comes to terms with being gay. Afterwards, Joey is supportive of Jack and the two form a close friendship that would last the series. In Season 5, when Jack speaks derogatorily of Audrey, Joey calls him out and while Jack is often seen to be the most perceptive and right in arguments and discussions in the group, as he possesses a grounded life view, Joey seems to be the most able of the gang to call him out on his stuff, perhaps due to the two having dated.
Jack and Dawson didn't get on well at first due to Jack's attraction to and later relationship with Joey, Dawson referring to Jack as the guy who stole Joey away from him. After Jack came out the two developed a friendliness, becoming especially close over the summer between Season 3 and Season 4. Dawson at one point even saved Jack's life, when Jack became severely depressed and binge drank to the point where he wanted to end his life. Jack jumped off the roof and into a pool, nearly drowning. Dawson pulled him out and Jack opened him to him about everything that has happened to him since graduating high school.
After Jack moves into Gramps' old room, Jack and Grams become something akin to family. Grams is very supportive of Jack in all aspects of his life and, like Jen, is not afraid to serve the smart guy with a bit of counter-wit when the situation calls for it.
Jack’s father; In the beginning he is a very distant father, supporting Jack and Andie only in an economical way while living out of town. Mr. McPhee is very unsupportive when Jack comes out to him, but by the end of Season 3 he accepts his son's sexuality and the two of them become much closer.
- Main article: Jack and Ethan
Jack and Ethan meet on a commuter train back to Capeside after Jack, Dawson, Andie and Joey spend the weekend in Boston. Jack is surprised to learn that Ethan's gay and they immediately have a connection, with Jack being interested in getting to know the first other gay kid he's met. They spend time together at a Capeside Festival and later Jack invites Ethan over to his house for the weekend where Ethan helps Jack with his strained relationship with his father. Jack feels that Ethan considers him a newbie, which Ethan calls Jack jokingly on occasion, but is worried that it'll stop Ethan from being romantically interested in him. Jack hesitantly asks Ethan to be his date at Prom, but they fight when Jack feels like it's just political for Ethan. Ethan confesses that he is interested in Jack, but that he's not sure Jack's ready for a relationship. Ethan leaves and Jack, encouraged by Grams, Andie and Jen, travels with them to Ethan's boarding school to see him. Jack finds him and, although he's nervous, he kisses Ethan. Sadly, Ethan has reunited with his ex and Jack leaves heartbroken.
- Main article: Jack and Doug
Jack and David meet through Jen and C.J.'s flirtation and become interested in one another. They go on a few dates and start a relationship. They do well for a while, but David starts feeling like Jack isn't into the relationship like he is.
Jack and Eric are members of the same fraternity at Boston Bay College and get along fine, until Jack decides to move into the frat house and is rooming with Blossom, an "upper classman". Jack finds it strange as Blossom used to have a room by himself and figures out that he was supposed to room with someone else. Jack confronts the frat about this homophobic treatment and they cover for Eric, but Jack figures out it was him. They make amends until Eric is about to make a move on Jack and Jack leaves. Eric then accuses Jack of having made an unwanted move on him, and Jack parts ways with the fraternity.
- Kerr Smith was hired as a character that would create a love triangle with Dawson and Joey