How to stop my kitten from suckling her sister's anus and her own?

Congratulations on your new babies! I adopted brother and sister kittens a few years ago. My male also displayed this behavior on his sister (as well as one of the dogs), but that behavior had improved by the time he was 6 months old. There isn't anything inherently abnormal about the behavior, and it's really only a problem if the female decides it's a problem, so I don't know that I would worry about it. I suspect that it will decrease quite a bit as he gets older and more settled in your house. The only other caveat that I will give you is that some cats will also do that on (especially wool) blankets and sweaters to the point that they chew/suck a hole in the fabric, so be on the lookout for that behavior. I hope that was helpful! Thanks for using Petco Pet Education Center, formerly Petcoach.

I would try to keep the kittens separated if the femal continues to try and nurse from the male. Right now the male appears normal but continued irritation could cause a problem. I would also recommend making sure they are getting enough nutrition because she may just be hungry.

This is a normal, comfort seeking behaviour in kittens and they will generally grow out it as they get older and there is no need to do anything to discourage it unless the skin is becoming damaged in which case you should separate them

What cute kitties! I would discourage this behavior by removing the kitten each time this occurs and trying to distract him with something else- a fun toy or treat. Also giving him some time alone so he develops some independent from his sibling can be helpful. A feliway pheromone diffuser may also be helpful if the suckling is a nervous response. You can also put a little shirt/sweater on the kitten getting suckled to make it tougher for the suckler to get to him!

This is usually not a hunger-driven activity in a 10 week old kitten. It can indicate that the kitten was weaned or taken away from its mother too early. I would definitely continue to prevent this behavior, as it can continue into adulthood and could cause problems like an infection in the mammary gland of your dog. You may have your dog wear a shirt to cover the nipples, or keep them separated unless you can monitor them. Since it can be brought on by stress, you can try supplements for stress such as Zylkene or Feliway/Comfort Zone Feline Pheromones. Here is some more information: https://www.petplace.com/article/cats/pet-behavior-training/wool-sucking/

He will stop doing it as he will be able to see and hear properly soon. Urine would be eliminated through gastrointestinal system anyway (so it is unlikely it will cause major toxicity). In few weeks he will definitively grow out of it. Check his weight constantly to monitor weight gain. Please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.

The kitten is likely still missing its mommy. Kittens normally stay with their mother until 10 to 12 weeks of age, but, unfortunately, humans take them away long before that. So your male's penis is the closest thing to a nipple to get comfort from (suckling is not just for milk but also for comfort).