Joyce Chalfen would probably describe herself as part horticultural expert, part supermom, and part superwife. She takes being a wife and mother very, very seriously. The most important thing to know about Joyce is:
She needed to be needed. She'd be the first to admit it. She hated it, for example, when one after the other her children, pop-eyed addicts of breast milk, finally kicked the habit. (12.9)
So when Irie and Millat walk into her house, she sees an opportunity to make some new people dependent on her: some kids who clearly need a mother figure, in her opinion.
Millat becomes the subject of most of her attentions for the rest of the novel. The more badly, he behaves, the more involved she becomes with him, eventually driving her own son, Joshua, away.
At first, Joyce seems to have it all together. She's all calm, cool, and collected, but life doesn't really work that way for Joyce. In the end, her need to be needed gets in the way of her judgement and her family life.