he should be kept seperate from around 2weeks before the birth, I never ever allow any males near my girls after this time, the stress alone could upset them.

id keep him seperate from now, I do this until the kittens are older then supervise any visits with the males, luckily they all seem to want to play and wash them, but I dont think you can ever be to careful

When I breed Orientals I had the same issue, Tiggy was always suggling up to Tito my neutered male, and she would follow him everywhere.
They stayed up untill she was ready to give birth, and then she was happy to be with her babies later. He must have missed her as he was looking high and low for her Love him
Afer a couple of weeks she let him come and see her kits and she would let him be around her babies, they all got on great, but that was my cats not all cats are like that...

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Jo & Luli Mei