My kitten is now 6 months old but my year old cat is having kittens anyday now and my 6 month old is try to nurse on her and he’s been doing that to his older brother who is also a year old. Why is he doing this he eats cat food and brings me dead moles and alive chipmunks.
It sounds like it's more a habit than to actually nurse at this point, seeing as he also is sucking on his brother. Sucking on things is actually a relatively common habit in cats, similar to the habit of kneading, although not as common as kneading.
If you notice the suckling is causing problems, or if you simply want to prevent the behavior, you can cover your other cats' nipples. An easy way to do this is using a large sock with the end cut off, if your cats are small enough. Or similarly finding some way to wrap up the cat's belly.