|Series 03, episode 04|
|Date aired||2 December 2005|
Sistering is the fourth episode of series 3 of Peep Show.
When Mark goes out with Sarah and Jeremy, he realizes that Jeremy is using "moves" on his sister, talking about being a musician and trying to flirt with her. Mark tells Jeremy he must promise not to try to sleep with Sarah. Jeremy says he promises to try not to sleep with Sarah, flipping Mark's words around. Sure enough, that night they sleep together.
When Jeremy and Sarah are out of the house, Jeremy's ex-girlfriend Big Suze arrives, and is a bit disappointed to find out that Jeremy has moved on. She ends up hanging out with Mark, just as friends, but Mark begins to develop feeilngs for her, eventually deciding he's in love with her. Big Suze, however, views Mark as a "harmless eunuch".
Jeremy, who is still in love with Big Suze, is annoyed at Mark for being in love with her, and begins to become disgusted with Sarah when he discovers she is exactly like Mark, noting that "she even smells like Mark". He realizes he's "basically got my penis inside of Mark" and no longer wants to have sex with her.
Big Suze comes over for dinner, where Mark tells her about Jeremy's love for Sarah, hoping it will turn her off of Jeremy and make her think he is permanently taken. When the boys hear Sarah crying in the bedroom, they battle over who has to go and comfort her, since neither one of them want to go. When Jeremy finally goes to see her, he finds out that she is crying because she feels guilty--she and Simon want to give their marriage another chance. Jeremy is thrilled, but pretends to be disappointed, and lets Sarah leave.
Mark is furious, partially because Sarah is his sister and partially because it means Jeremy now has a chance with Big Suze. Sarah returns shortly, saying that she went to meet Simon only to find texts from another girl in his phone. Jeremy is stuck with Sarah, meanwhile Mark tells Big Suze he isn't in love with her, and doesn't even like her that much, partially for Jeremy's sake and partially to avoid embarrassment.