Jak is the angsty and loyal team member of Team Sonic.
Jak has had numerous relationships with other characters throughout the series. The first, and perhaps most significant, is the secondary protagonist, Jak's sidekick, Daxter. Jak and Daxter, while both sharing a titular role in the game, have been close friends throughout the series. Arguably, it is Jak that is responsible for Daxter's transformation from human to ottsel, which set the stage even further for Daxter's role as a "sidekick". As noted by one of Naughty Dog's developers, Daxter and Jak's relationship is inseparable, which was brought to further light in Jak 3, when Daxter stayed behind with Jak in the desert, and likewise, Jak stayed behind with Daxter towards the end of the game. Additionally, Daxter spent two years looking for his close companion while he was imprisoned, in addition to showing multiple signs of loyalty to him.
When they were little, before he met Daxter, they were best friends forever. But Darrienne took Jak away and send him to the future, but luckly he escape. He didn't know that Julie was his best friend until his father's untimely death.
He and Sonic are really great friends.
He and Ryuko are really close friends, but somehow during Sonic Storm Adventures of Kill la Kill, they begin to have feelings for each other.
Jak take cares of his half-sister.
Jak take cares of his little half-brother.
Jak is a very good friend to Sora since they met in prison.
Jak did not have any relationship with his father due to their loss of contact since Jak's infancy. Shortly after Damas passed away due to a fatal accident in the Slam Dozer after battling a league of Dark Makers, Jak suspected that Damas was his father after he asked him to find the child heir to Haven City, which Jak already found out was himself as a child. Shortly after observing this, Darrienne tauntingly confirmed Jak's supposition.
Jak has always been with his mother since he was born, but lost contact when he was taken by Darrienne at the age of 4. In The Broken Hero, Jak is reunited with his mother once again. In The Death of a Lost One, Jak saw Monglia get killed by Darrienne and completley sobs over her when she passed away.
When Jak first met Elaine, she thought Jak was her father, Lukas. So Jak has to pretand to be Lukas. During his time on his adventure, he and Elaine bonded for a little while. When he escape from the clutches of Seler, Elaine discovered that Jak is not Lukas, no thanks to Daxter. Jak then gets angry at Elaine and yells at her for being stupid, which made Elaine cry and run off. Jak finally realizes that he has grown to love Elaine and wants her to be his daughter. When he went to rescue Elaine from Seler, Jak was already too late when Elaine died from all the Dark Eco Seler pumped into her. Jak began to cry over Elaine and he told her that he loves her, making her come back to life. She has been Jak's adopted daughter ever since.
Jak never really liked Jade due to her stubborness, but after getting to know her, she has become Jak's female best friend and always been by her side, but sometimes gets annoyed when she doesn't want to do anything.
Jak trusts Annie and she is his best girl friend. (She is Jak's best friend and Annie's a girl)
Jak and Jumpy are good friends.