J.D. and Elliot go to pick up J.D.'s son, Sam, from Kim's (Elizabeth Banks) house. Apparently every time jealous Elliot even sees Kim touch J.D. (to fix collar, remove lint, etc) she makes him have car sex on the way home. Score! Meanwhile, J.D. gets to see his own jealous side when it turns out Elliot's ex, Sean (Scott Foley) is dating Kim! Apparently, Elliot introduced them over a year ago to each other.
J.D. had to deal with his jealousy and attempt to befriend Sean while Elliot and Kim bonded over sex talk, etc. It doesn't go so well and the animosity continues. In the end, they go over all the awkwardness by bonding over watching a video of Sam. J.D. decides he wants to move closer to Sam (apparently a 30 minute commute is too far for this jack ass). The episode title, "My Cuz" stemmed from the term, "weiner cousins" because they shared women.
Meanwhile, Kelso catches a stomach virus from the pastry chef at the Hospital coffee shop. He's admitted and tries to diagnose himself but Carla puts the interns on him.
Cox announces he's looking for a new Chief of Surgery, and Turk is determined to get the position. Cox's hatred of "Ghandi" makes him refuse to see that Turk is the best choice. Turk ends up sending in every surgeon to Cox's office to convince him to hire Turk. However, in the end, it's actually Kelso who convinces him to hire the person who's best for the job, not who he likes. As Kelso points out, he never got along with Cox but kept promoting him because he was the best.