A Dog's Breakfast (2007)

Synopsis
If you've never been good at anything in your life, why would murder be any different? Patrick has always had a somewhat combative relationship with his little sister Marilyn. But when she brings home her new sci-fi-soap star fiancé Ryan, it's all out war. When Patrick fails to drive a wedge between the happy couple, he reaches for sharper instruments. Every family has a few skeletons in the closet; A Dog’s Breakfast is the nightmarishly funny mess Patrick makes when he tries to add another to his. ~adogsbreakfastmovie.com