Who Is Gon's Mum?

At the end of the tape, when Ging was going to tell him about his mother, instead of listening to it to the end, Gon just stopped the tape and stated that Mito was his mother.

Is Bisky Gons mum?

So you know how Bisky had that weird response when Gon asked her if she knew ging? Also, when she said goodbye to him after the greed island arc she said something about missing wanting to be around him like a mother or something like that.

Is hisoka related to Gon?

Yes, in the Hunter Chairman Election arc, it is clear that basically everyone who is a licensed hunter knows that Ging Freecss is Gon's dad, including Hisoka.