My Boy cat is neutered but he's still licking my female cat's butt. Why?

Since the mom was spayed 6 months ago, it is pretty safe to say that this butt licking thing doesn't have anything to do with them being ready to mate. She is no longer producing the hormones that would cause her to emit pheromones to stimulate the boys' interest.

This will probably continue until the mom teaches them to stop. Her hissing and scratching at them is her way of telling them No.

It will take some time (a few days to a few weeks) for the "male hormones" to leave their systems. Although, I really don't believe it has anything to do with the licking.

Sometimes male cats who are neutered behave like female cats. They will demonstrate nesting behaviours, carrying behaviours and even kitten rearing behaviours. He may be trying to enact what a mother cat would do with a new kitten - clean her well and keep her bottom from being messy. When she gets older (8 months to a year) he will probably cut it out - but for now this is allowing them to bond. If she doesn't mind it and he's not hurting her (doing it to such excess that she's trying to hide from him), you may allow it to continue. Nudging them apart when he wont cut it out or holding them apart (but not putting them in separate rooms) should help him find some boundaries with her.

If the female cats are not spayed, keep them separate. His neutering took out the main parts but his 'plumbing' still has viable sperm in it for about five days and he can get her pregnant.

His testosterone levels take over a month to go down so he'd still be responding to her. It's up to you to make sure he doesn't mate with her for at least a week.

All of my cats, which are all spayed/neutered, lick each other's butts. I think its just another way they groom each other and gain information about each other via scent (since they usually smell before they lick)

it takes about a month for hormones to leave the males bodies,even then it may continue,they may just be trying to bond with their mom,my cat licks his sister (only he licks her head) thank you for having your cats neutered and assuring that they dont contribute to the thousands dying every day :)

My cats are 14..they have been fixed since 6 months old..they are brother and sister..he does this to her constantly..it's a cat thing and it's harmless.

I'm sorry to tell you this but... Your cats are whores and like incest

WHat? he cant give his mom oral? i think he love the stuff.