Suggestions for FWK re integration

[Allergictoironing]

Tax attached of 2 kittens (now 5 months & comfortably over 3kg) and Tortie older resident.

FWK is a little concerned about the integration of the kittens with the existing cat. Been 2.5 months now, and existing tortie is still hissing, growling & swiping at the kittens, sometimes with no apparent cause. So far no claws seem to be involved, no blood or tufts of hair, no biting, but she seems to be taking quite a long time over accepting them. No hissing or swiping from the kittens at all.

They were kept separate for the first couple of weeks, then kittens restricted to living room/kitchen area and older cat full run of the house. Fed separately. 2 litter trays for cat upstairs, 2 for kittens downstairs. FWK mostly works from home, cat & kittens not allowed to mingle when he's out.

He's asked me to ask you lot a) does this seem a reasonable time or a long time for tortie girl to accept the boys, and b) any suggestions.

Maybe it's just the Tortie being full of tortitude?

She just feels that she must always tell them that she's the boss and not to fuck with her or else!

My girl cat still growls at most of our boy cats six years on. She's absolutely fine, just mouthy.

It’s a Tortie, he’s lucky to be alive.

I’m having the same issue, only with all adult cats. I think it’s the two vs one issue. Where the cat might have adapted more quickly to one kitten, two is more stressful. Also, females are more territorial than males.
I feed mine together and give treats together, and I’m seeing improvement. I seperate them if there’s repeated hissing/one is getting too stressed.
I’m still seeing outrage that Another Cat is in Her Space after 4 months. She runs up to him when he’s sleeping peacefully and whacks him on the head.