I have two cats, Both of them are females and sisters from the same litter. So, they have been together ever since birth. One of them recently had kittens and now when the other cat sees her around the house all she does is hiss at her and try to scratch at her. I know it may be because she doesn't recognize her scent. But my question is how can I get her to stop hissing at her sister? And now that the new kittens are here how do I get her to accept the new kittens?:confused:

Its hormones and instincts driving her right now. Its natural for her to want to protect her babies. You might just want to keep the two cats separate for now until the kits are older for every cats safety.

Its not the mother cat that is hissing though, its her sister the one that didn't have the kittens that keeps doing it. The one that had the kittens seems to be OK with her and will actually try to go near her and even allows her to go fairly close to her kittens but it's the other one that keeps hissing at her.