I'll get right to the point. The two cats I'm petsitting are siblings but for the past month or so, I've noticed that she male cat likes to lick the females genitals every chance he gets. She tries but I haven't seen her do much more. She normally really aggressive with him because he gets too close. Last night, I was woken out of my sleep because of loud meowing and hissing. The female cat was pinned on her side and the male cat was on top of her trying to what seemed like mate with her. She clearly didn't want it because she kept laying on her side and she was hissing at him, hitting him and biting him. She was also clearly crying in distress. Why does this happen? Is it a behavioral thing or medical? Should I tell the owner?