Kevin Myers is the initiator of "the pact" for the guys to lose their virginity before they finish high school. He tries to repair his relationship with his girlfriend Vicky after they have a serious fight at the party when she accuses him of being with her only for sex. Eventually, Vicky gives in and the two lose their virginity to each other. When his older brother gives him the Sex Bible in American Pie, Kevin uses this knowledge to unleash the "Tongue Tornado" on his girlfriend Vicky. The couple ends up calling it quits, and when we see him again at the beach house with Jim, Oz and Paul Finch, he is still broken up with Vicky. Unfortunately, he is still hung up on his "first," and ends up putting the moves on her time and time again despite the massive numbers of hot babes around every corner (and right next door). By the end of the film, he seems to have finally manned up and gotten over his ex, but this is only an assumption.
When he returns in American Wedding, it's revealed that he has a new girlfriend, but we never learn who she is (presumably, his wife Ellie). He also plays a much smaller role and has scanty screentime in this film, and has no relevance to the plot.
In American Reunion Kevin has now got a wife and is a stay at home architect (though in American Wedding, he mentions going to law school). He and Vicky are shown to be still friends but when he wakes up naked in bed with her. He accuses her for sleeping with him, Vicky is disgusted that he thinks that she could sink so low and tells him nothing happened and they never slept together. At the reunion, Jessica gets Kevin to apologize to Vicky, who is upset. He apologizes to her and they make up and remain friends, Kevin's wife appears at the reunion and gets Vicky and Kevin to dance with her.
"Separately, we are flawed and vulnerable, but together we are the masters of our sexual destiny."
"No longer will our penises remain flaccid and unused! From now on, we fight will for every man out there who isn't getting laid when he should be! This is our day! This is our time! And, by God, we're not gonna let history condemn us to celibacy! We will make a stand! We will succeed! We will get laid!"
"Finch, you don't think there's one girl you're destined to spend your entire life with?"
"Can somebody please untie me?!"