My cat's a pervert

[Sollers]

I have two gorgeous cats, who are brother and sister and were adopted from a rescue at 8 weeks' old. They were both sterilized early on, in accordance with the agreement we had with the rescue centre. They are now about twenty months.
The problem is the boy cat is now regularly pinning his sister down and simulating sex with her. My girl cat hates it and will spit, hiss and smack him until he stops.
Should I intervene or leave them to sort it out between themselves?
Boy cat is quite a bit bigger than girl cat, but she is capable of defending herself.

Part of me finds it a bit funny, because "WTF, boy cat, you've got nothing to put in there anyway?! And she's your sister, you giant perve!" But I'm also a bit worried about girl cat's wellbeing. What should I do, wise MNers?

Taser him, the filthy animal!

I hope someone gives you a sensible answer soon.

I have the same problem, but it's the kitten trying to hump his male house-mate and his furry cuddle shag bag.

They do still have their bits and are capable of DTD, just no "pom poms", so if it's upsetting her intervene.

Yeah was going to see he will still have something to put in, they don't remove that bit!

My boys used to do this to their sister. They continued to do it for about 6 months after they were spayed then stopped. Maybe yours will too. How old are they?

Oh! I feel a bit dim now, I didn't realize he still had some bits. (He is very fluffy, and I have never thought to look there, ok? ) anyway, he doesn't seem to be doing anything with it. Just what I used to call dry humping when I was a teen.
i have also just realized they're not the 20 months I mentioned in my op. They are in fact nearly 3. (No wonder my boy is a sexual deviant with such an ignorant and forgetful mother. ) So they have been done for over 2 years now, but it's only in the last few weeks that this has become a regular thing.

That is a bit weird as hormones and stuff should have calmed down by now I would have thought. Not sure what to advice really I would def tell him off for it though.

Cat 3 (11-12yo) regularly shags my arm, sigh.

It's a dominance thing. My neutered male didn't start doing it until he was about 4. It started one day when I was wearing a black and white floofy onesie. Then unfortunately the kitten learned the habit from him.