It's a long time since I posted that one. The 'kittens' are now all grown up. My elder three cats are all a bit tubby. I have changed vet now and he isn't concerned as they are healthy for their ages. The 'kittens' are the correct weight and Tabitha and Tigger are still very slender, but not worryingly so. I now try and feed them separately. They are healthy and happy.
Tigger was neutered as soon as the vet would do it as I was terrified he would get his sister pregnant. Tabitha was spayed once her kittens were weaned - eight cats is quite enough

Tigger has always wandered, yet when he comes home he is a real softy, loving his cuddles and purring and purring.