Neutered male trying to mate

Hi guys, question for you. All our cats are neutered, the 3 girls as well as the 4 boys. The kitty in question was neutered at the same time as his brother and sister, after their sister's first heat cycle. Anyhow, Bender wants to do the deed, but he's a little confused at times. He usually goes after his sister, and she puts up with him for a while, but then growls and hisses and runs and hides, with him in hot pursuit. Well this morning I was eBaying and I heard this growling whine behind me and it was Bender on top of Grayson, his brother. Bender was biting into his neck pretty well to hold him down and was doing the kneeding thing with his back legs and humping poor Grayson's back (which is all he ever does with his sister anyways), and Grayson finally got away. But Bender won't let up until he "finishes" or whatever it is that happens in neutered cats. The problem is, Bender is one of the sweetest, most loving cats, to us and all the other cats. But when he gets in "Humpy" mode (Humpy is his nickname sometimes...) he turns very aggressive in typical unneutered male cat behaviour to whoever his victim is. The funny thing is, up until this morning it has always been Carmel he goes after. Why the sudden change to Grayson? Anyway, long story short, our household is always peaceful with the 7 cats, until Bender starts doing this with Carmel or Grayson and they run away and hide under the china cabinet where Bender hits them to try to get them to come out, and screaming, hissing, growling, etc. Ugh Bender just chased Carmel under the bed here in my office...My question is, should I step in and give Bender a time out in a room by himself, or just let them do this? He is not hurting anyone (well not drawing blood or making hair fly) and it seems to be more of an annoyance to the other cats than anything else. It's just the only time in this quiet household we hear screams and whatnot...Your advice is appreciated.

Sarah, it sounds like Bender is trying to show all the others that he is the dominant cat. The pseudo-mating behaviour is an indication of this. it may be time to invest in a Comfort Zome plug-in. You can read about it here.

That sounds like a good interpretation.

My Squirt is 8 years old and neutered since kittenhood. Every spring, he goes through the mating ritual with Joey, same stuff you describe. So, I think partially it may be the season, too. But in my house, the younger cat (Joey) seems to be the Alpha, except when Squirt asserts himself in this manner.