I admit, I was screaming when I saw that scene (especially since it was right after this nice action packed sequence...). Thank goodness I was alone at home at that time, although my neighbours may have been wondering why there was someone screaming, "NO! OMG! Not the pool table! They did IT on the pool table!" And random variations of basically the same thing.
And yeah, I guess I was jealous (or maybe disturbed?) because there was this gut-wrenching, stomach-twisting feeling throughout the scene. And I agree, they're more like brother and sister. Seeing them in 'bed' together is wrong - to me.