They started dating soon after meeting, however it was subsequently revealed that Joaquin was merely associated with Kevin on the instructions of FP Jones, as a method for the Southside Serpents to maintain eyes on Kevin's father, the Sheriff. Despite his directives, Joaquin developed genuine affections for Kevin. This became evident when he tried to protect him from an attack by FP's goons.
Later on, when Kevin decided to leave town with Lila Tournay, Joaquin went with him, since he didn't have anyone else in Mexico who loved him. During their time away from town, they fell in love and planned to run away together but were eventually caught by Kevin's mother, Anita. She wanted her son to be with someone responsible so that he wouldn't be killed by his father. At first, Joaquin refused to give in to Anita's demands, but later agreed to return home if Kevin stayed away from town for three months. When Kevin returned without having left town, Joaquin did not appear at all grateful for being allowed to stay and was seen barely speaking to Kevin. This showed that despite their relationship starting out friendly, there was something more than friendship between them.
After this incident, Joaquin stopped appearing on screen completely until one night when Kevin comes home late from partying and finds Joaquin lying in wait for him with a gun.
Kevin soon discovered Joaquin's lie, as well as his role in the cover-up of Jason Blossom's death, and the pair split up after Joaquin left town. However, they remain close friends.
Kevin has had relationships with several other people since then, but he has never married or lived with anyone for more than a few months at a time.
In April 2010, it was reported that Kevin would be getting a new boyfriend named Andy Dufresne in an upcoming episode of Teen Wolf. The episode was supposed to focus on Scott's attempt to prevent another murder by going back in time, but it was revealed at the end of the episode that Andy is actually a shape-shifter who takes on the form of Kevin's former friend Joaquim. Their relationship will continue into season two.
Joaquim first appears in the episode "An Evening With A Dead Man", which airs on May 5, 2011. He and Scott bond over their experiences as prisoners at Pinehurst State School for the Criminally Insane before she reveals herself to be alive and well. After this revelation, Joaquim leaves town, but not before telling Kevin that they need to meet up again someday.
During their stay in the Desert Otherworld, Kevin appeared to be quite fond of Carlos and was genuinely distressed upon reading the note Carlos left for Kevin at the radio station. Kevin is quite fond of Charles and thinks he is incredibly handsome. Additionally, they both like playing guitar so it's not unlikely that they would get along well.
Kevin has been known to fall in love with someone he meets only once before leaving home. This happened when he met Lara at the radio station while searching for his parents. Although she was married at the time, he fell in love with her and didn't stop thinking about her after he left. Years later, she was killed by Drogo when she was just a young girl. Now, given how fond he seems to be of Carlos, it may be possible that he could end up doing the same thing with him.