Hissing issue!

[McBounty]

We have two beautiful kittens. One boy, one girl and they're siblings. They're almost 6 month old.

We have a problem with hissing.
If we go to give them both a piece of chicken or a treat, they instantly hiss at each other to warn each other to stay away. Our girl does it when she's playing with a toy too. If she has the toy in her mouth and she's playing, she will hiss at her brother for just watching her play.

I've noticed they no longer really acknowledge each other and when they do, they play fight until one of them cries as they other has clearly gone too far (I think).

How do I deal with this? I'm so worried they won't be very good companions as they get older.

They're both neutered/spayed already and have been since just after they hit 4 months old.

I have two sisters. One is very hissy. They will never be best buddies. I give them space. Feed separately. They tolerate each other!

Perfectly put when it comes to my two. They tolerate each other.

They've never liked sharing from the moment they came to us, but they still cuddled up to sleep and groomed each other. Now they just pass by each other and will sleep close by, but never together anymore. It makes me a little sad actually.

Our girl is the one blissfully sleeping.
Our boy is the darker, chubbier one.

Our boy. 😊

@McBounty I had two siblings that didn't get on. Basically they hated each other rather than tolerated tho! Just gave them space and fed in two different places in the kitchen to minimize conflict. They had a big house and garden, they didn't have to ever really be in the same space.

OMG that fluffy tummy is delicious!