Throughout the SeriesEdit
In The Party, Kevin throws his husband a birthday party and invites his colleagues at the Nine-Nine, who assume that Kevin invited them because Holt didn't actually want them there. When they arrive at the party, Kevin is instantly curt and snobby to the Holt's colleagues. He also continuously needles Peralta and making him uncomfortable. Later Kevin and Holt start fighting about how Kevin is acting around his guests. Jake, Amy and Terry are hiding in the bathroom and they learn that Kevin only invited them there because Holt asked him to. Kevin and Holt ask them to leave. Later, Jake realises why Kevin wouldn't allow cops. Kevin dislikes cops because of the way Holt's former colleagues discriminated against him for his race and sexuality. When Jake plans a private evening for Kevin and Holt, his feelings toward the detective seem to soften, and they even play a small prank on Holt together: Kevin asks Jake to call him "Kev," a nickname Holt knows he hates.
In The Mole, Kevin briefly appears when Jake comes to their house to find out who the mole is with Holt. Kevin calls Holt stating that his "work life is here".
In Stakeout, Kevin appears when Marcus and Rosa emerge from his bedroom. Kevin conceals a smile at the situation and invites them to come and join them for breakfast but Rosa feels awkward and leaves.
In The Wednesday Incident, Jake and Gina ask for Kevin's help in finding out why Holt has been in a bad mood. Kevin agrees to help and they talk to all the people Raymond would have seen before work such as Diane, his fencing partner and his fellow painters. However, when they talk to his fencing partner, Kevin finds out that Holt hasn't been there since last Wednesday. He leaves and is upset, as Holt said he had been fencing and he had lied to him. Jake later thinks that Holt was mugged and goes to tell Kevin. However Holt comes in and reveals that he fought the men off and was "lightly stabbed" as a result. Kevin is annoyed that Holt lied to him and Jake leaves after being reprimanded by Holt. Later, Kevin appears with Holt and gives Gina and Jake some still life paintings of a grey rock that Holt has done as a thank you.
In Boyle-Linetti Wedding, Kevin attends Darlene and Lynn's wedding with his husband. Holt remarks that he might like to have a more public expression of their love, as their own wedding was short as they didn't know how long gay marriage would be legal for. Kevin tells him that if they had had a bigger ceremony he never would have heard Holt's efficient/officiant quip and Holt agrees that he regrets nothing.
In AC/DC , Kevin invites Marcus and Rosa to have dinner with them. Upon arrival, Kevin calls Marcus into the kitchen to help him with the food, leaving Rosa and Holt alone. During the dinner, Kevin attempts to converse with Rosa and she keeps her answers short as to avoid becoming too personally acquainted with Holt.
In The Swedes, he leaves for Paris to teach at the Sorbonne for six months. Before he goes, he and Holt ask Charles to take his place in a squash tournament as they have won for the past few years. Later, over video chat, Kevin congratulates them on winning and says that he is looking to forward to winning next year but Holt says they can't as due to Charles's wild behavior, they are banned for life.
In Skyfire Cycle, he and Holt are arguing about the "Monty Hall Problem" which Kevin brought up during their first dinner together in 2 weeks. They tell the problem to Rosa and Amy wherein Holt's decision is to stay with the original choice while Kevin says the odds are better if the decision was changed. They continue arguing about the problem. Later on, Rosa concludes that they're arguing because of the night shift and are simply sexually frustrated. By the end of the episode, Holt says the problem is fixed and it turns out, Rosa was right, to Amy's dismay.
In Safe House
In Two Turkeys
Kevin is shown to be quite serious and intellectual as he is head of classics at Columbia University. He can also be quite curt and some would view him as snobby, such as his dismissal of the nine-nine, in particular, Jake. However, he does later soften to the detectives, even playing a small prank on his husband with Jake. He also shows a softer side around Holt and Gina as he is kind and friendly around them.
Holt is Kevin's husband. The two get along very well and care deeply for one another, such as when Kevin wanted Holt to tell him everything particularly if they were worrying such as Holt being lightly stabbed. Kevin also considers Holt the funny one. For example, even when they were fighting he found Holt's play on words about needling Jake a new suit hilarious and told him to stop being the funny one. Kevin and Holt met while Kevin was writing an article about Holt for the New Yorker and Kevin said that Holt's answer had him in stitches.
Jake and Kevin have a complicated relationship. Although Kevin doesn't dislike Jake, Kevin is not fond of cops due to the discrimination Holt has been subject to from detectives who looked very similar to Jake. However, the two seem to have a neutral relationship later as the two agree to play a prank on Holt and Kevin gives Jake and Gina paintings. Kevin also thinks that Jake is extremely juvenile, serving him soft drinks whilst others get wine.
Whilst Kevin's relationship with the detectives remains distant, he does become on a first name basis with Gina. Jake and Gina help Kevin figure out that Holt was mugged on the way to work one morning. Gina and Kevin appear to be on good terms as he is willing to accept her advice even if he rejects the same advice from Jake.
Kevin is close with his husband's nephew Marcus, who stayed with them, and he tried to learn more about Marcus's girlfriend Rosa when she came over for dinner.
- The name Kevin "Cozner" is very similar to actor Kevin Costner. Costner is well-known for his role in Dances with Wolves, which is why Jake asks whether Kevin is the star of "Danzez with Wolvez".
- His brother is the best oral surgeon in the quint state area.
- In The Swedes, he leaves for Paris to teach at the Sorbonne for six months.
- Holt claims that his watch in the Halloween episode of Season Two is a gift from Kevin's father just before he died and thus holds a great deal of sentimental value. As this information was stated in the wider context of a bet there is a chance that it is false. There is further evidence for this being false information in the episode "Mr Santiago". Holt admits that he was very arrogant when meeting Kevin's parents for the first time and blames his overconfidence on why they do not approve of their relationship (as well as the fact that they are huge homophobes and believe Holt made Kevin gay with his "magic genitalia").