Manny & Lo (1996)

Two sisters, Amanda, 11, and Laurel, 16, run away from their different adopted parents, sleeping in model homes, or wherever they can. But when Laurel becomes pregnant, they find they can't make it through this crisis on their own. With nowhere else to turn, they decide to kidnap Elaine, a clerk in a baby supply store. But Elaine seems to need Manny and Lo just as much as they need her.