Does Foolkit have a good relationship with his dad or is Tempest an absent father I’m guessing the second one though I hope it’s the first
so you're not wrong that Tempestmask is primarily just absent. I think Foolkit looks too much like his ex, and he's definitely like. Feeling regret for lashing out at the poor kit, and naming him Fool, but not only feels like it's too little too late, but gets so angry at himself that the cycle of selfhate-> taking it out on others just continues. He self isolates, broods, spirals, and leaves most of the kit rearing to Laureldapple and Hollowstripe - who like Fool enough, but don't really see him as their own son the way Slate is.
I also think Tempestmask just doesn't really like kits in general, his relationship bars with almost all the kits are negative until they become warriors, with the exception of Posy who he was mostly fine with. So there's hope as Foolkit gets older!