Silva isn't a bad father his family are Assassins so they are raised to inherit and take part of the family business. We've seen their relationships it mostly give and take amongst the men but everybody loves each other...Except for Alluka the Satan spawn Lml . And Killua's feeling towards his mother (this should be explained more). They simply kill as a trade and mostly bad Ppl are killed, like Killua said "why would somebody want to hire the best Assassins to kill you in the 1st place?"
The whole Zoldyck family are like their own little enclave, and if any of their children even think of escaping, there are going consequences to be had (i.e. beating and torture). And from what I understand, although Silva is present, it doesn't seem like he really interacts his children in the capacity that a father should. Maybe he's around for training and being the family head, but aside from that, it seems like a lot of the caretaking is left on the shoulders of the butlers, and if I recall correctly, Illumi is the one who trained Killua to be an assassin.
I speculate that Milluki and Kikyo took part in a lot of the torture and beatings when it comes to Killua, hence why he seems to dislike them the most. Overall, I can see why he's envious of Gon's relationship with Mito.
And I can't sympathize with Gon, but I think Ging just wasn't quite sure what to do with a kid. He had his dreams to follow and I imagine it's difficult to be a hunter and take care of a son (and we all aren't sure about Gon's mom). I can't hate Ging for following his dream, but I can't respect him as a father due to his negligence. Though I am very curious to see how Gon and Ging's relationships develop now that the two finally sat down and had a discussion. What I find most interesting is that Gon never calls him "dad", it's always "Ging". And then Mito is "Aunt Mito". Poor Gon.
Only the parents would die for their children in the Zodlyck family; If they are still children under their care as Silva and Zeno left Killua during the Chimera Ant, who knows if Zeno knew about the bomb or simply had faith in Killua or left him to his fate he choose as a man. The family isn't normal or is the way they show their love. But Yes Butler's are the care givers to the Zoldyck Children but we've seen that the children have grown up together. Milluki plays his role as big brother and is simply jealous of Killua and enjoys torturing him, Illumi is flipping crazy. Kalluto jealous of Alluka cause Killua probably missed him too much to payed Kalluto lil attention.
They have strict rules placed on the kids until they've become mater Assassin's or attained a certain Lvl of skill to be set out in the world and fend for themselves. These rules also protect the family, even though some decision have ulterior motives such as letting Killua keep watch over Alluka; His father knows Killua has a fricking genie with him it's better to just let him do what he wants. Illumi is the most messed up as he's just very twisted but would have died for his family during his last confrontation with Killua in the hospital. Killing one another seems very unlikely except for Killua who is ashamed of his heritage or if it drastically applies to Ppl like Illumi if he tried to cross the family.
Silva head of the family is following tradition. Protect and raise the Assassin's until they can function traditionally on their own. He's also trained Killua all of the older Zoldycks did besides Maha. Ging did nothing for Gon but create a game that he never knew his child would play he took a gamble. Silva does and did more for his children than Ging has or probably ever will. Ging's love is more than tough it's insane.