Who is Rita, Astor, and Cody from Darkly Dreaming Dexter and what is their importance?

Rita is Dexter's girlfriend. Rita was married to a drug addict, who abused her terribly. Rita is paranoid about sex and afraid to allow Dexter to touch her. This is the perfect woman for Dexter since he has no interest in sex. Rather than spend time in romantic clutches, Rita and Dexter spend much of their time in athletic pursuits. However, one night when Dexter is emotionally excited by the Tamiami Trail killer, he and Rita are intimate. Dexter is disgusted and confused by his reaction to Rita.

Astor and Cody are Rita's children. Although Dexter cannot feel emotions for adults, he has a special place in his heart for children. Dexter adores Rita's kids and feels he could give or take Rita, but he would desperately miss her children should Rita throw him out of her life. Dexter sees how the children's father's behavior hurt Rita's children, so he wants to be a good role model for them in order to prevent any further damage. Dexter does not want Astor and Cody to turn out like him.