Suckling - do I need to stop this behaviour?

[seriouslynonames]

We have 2 kittens, litter mates, a boy and a girl. The boy is a little bigger and heavier but the girl gives as good as she gets when they play fight. But when they snuggle up for a nap the boy often (though not always) starts to nuzzle and suckle on girl kitty's nipples as if he's feeding from mum. She doesn't seem to like it that much yet also doesn't always miaow in complaint. I have been separating them when I see it happen but obviously am not with them for every nap/night time. I hope I am doing the right thing by separating them as it doesn't seem like a behaviour to encourage - they are about 12 weeks so not that long until we need to get him (then her) neutered. But he always looks so sad when I separate them. She is definitely more happy go lucky, he is more cautious in general. Any thoughts? Should I always get them sleeping separately, at least until the habit is broken? Or just separate when I see him suckling?
Thanks for your collective wisdom!

Sorry I cant offer any help but my 16 week old ragdoll kitten has been suckling her side since we got her but it is teamed with purring and lovely padding on my arm or chest. I read that it came be a sign of distress or a sign of contention, I am assuming the latter in her case. Watching with interest for advice though.

I’d leave them to it. Girl cat will stop him if she doesn’t like it, and he’ll grow out of it. If he’s getting some comfort from it for now, and she is tolerating it, then I wouldn’t intervene.

My little boy cat was doing the same to his sister and has really only just stopped at 6 months old. I'm not sure if it is a coincidence or not, but it stopped just as they were both neutered. We never attempted to stop him, as we figured she'd make it clear if she was too annoyed.

I've read that it can happen if they were separated from their mum before they were ready - I'm hoping that's not true as it's just too sad!

Similar here, we adopted brother and sister kittens last year and he was constantly trying to suckle on her. Spoke to the vet and she said he was probably weaned too early and would most likely grow out of it. Sure enough he did, it got less frequent and eventually he stopped altogether at about 8 months. His sister would bat him away if she got too annoyed. They were both neutered at 12 weeks so wasn't anything to do with that. I think it was mainly a self-soothing behaviour for him.

Thanks all. We got them at 8 weeks old and they were with their mum until then, so I don't think it was unusually early to be separated. It was from a rescue/foster family. He definitely seems to be seeking comfort, but I have been worried about her getting sore. I'll keep an eye for now. The vet has said we have to wait until about 5 months to get him neutered, am just hoping there is no chance of any accidental new kitties before then! I was hoping to get him done a bit earlier (he is bigger and heavier than her even though same age).

8 weeks is a bit soon. Recommended is 12

We had a cat (we got her at 10w) that suckled on our fingers -initially any exposed skin, and we taught her to use fingers instead. She also kneaded us at the same time. It got less and less over the course of a year or so, but seemed to make her relaxed and happy, and she occasionally did it throughout her life. I'm not sure I'd let her do it to another cat though, especially if they aren't happy about it.

You could try getting him a really fluffy blanket or sheepskin, he might find some comfort in kneading and suckling on that instead? My boy quite liked suckling on my fluffy dressing gown when he was tiny!