I don't think Big Tom is related to the kittens who live here. He bears no resemblance to any of them.
I don't know if he is a tom or entire but is an excellent surrogate parent, making sure the kits get fed and calming them in the presence of their ever-more-hostile mother.
Big Tom is HUGE, gentle and has long, thick mottled brown fur,
Mother cat is tortoiseshell.
Kittens were one short-haired tabby, two black & white & three short-haired ginger.