Bailey is a possible twin brother of Hayley and an older brother of Steve Smith. He was revealed in "White Rice" when Francine wanted to get him and Hayley vaccinated but Stan said no.

Although not further confirmed, the existence is possibly hinted at by Roger in the earlier "Spring Break-Up" when he states that Francine has had 3 kids, but this was dismissed as Roger's mistake because Francine gave birth to a third child in "Surro-Gate" but the baby, Libby, was not her biological offspring. In "Roger's Baby", she states that she had been pregnant four times, although this fails to confirm if she considers Bailey a separate pregnancy.