Zia is the daughter of Milhouse Van Houten and Lisa Simpson. While born in wedlock, she uses the surname of Simpson. According to Milhouse, Zia inherits most of her DNA from her mother, which given her appearence, makes sense.

Zia is much more rebelious than Lisa, with Lisa often making the comparison between her and Bart, this leads Lisa to feel as if Zia doesn't respect her at all, Lisa later finds outs via going through one of Zia's favourite hobbies, she finds that Zia actually does respect both her parents, but Lisa moreso than Milhouse.

Zia's favourite hobby is to go online and browse the Ultranet, which is the more advanced version of the current day internet. While still technically browsed through a computer, a cable connects to a port in the users neck, which causes their physical body to lose consiousness.