Who is Joey from Earth Abides and what is their importance?

Joey is the youngest child of Ish and Em and has a twin sister, Josey. Ish admits that he's not particularly bonded with any of the children though he talks of wrestling with them on the floor when they are children. Joey is a frail child and unable to keep up physically with the other children. However, he is something of a brat, according to Ish, when it comes to lording his intellect over the others. He sometimes seems not to want learning for learning's sake, but to show the other children what he can do. Joey is among the five who succumb to typhoid when a man named Charlie comes into their midst and spreads the disease.