Malcolm & Eddie (1996)

S1E6 Little Sister

Malcolm is eager to ask a stunning woman out at the bar, but he soon discovers she's actually Eddie's younger sister. Upon learning this, the roommates strike a deal that their evening will remain strictly platonic. However, Eddie's overprotective instincts kick in, and he makes it clear that he will be keeping a close eye on the situation, ensuring that his sister is safe and sound.