Stewart Gilligan Griffin, more commonly known by his nickname "Stewie", is a fictional character in the animate television series Family Guy. He is the youngest and the smartest (though, as an infant, he is frequently naive and misunderstands things) child of Peter and Lois Griffin. In addition to siblings Chris and Meg, Stewie has a half-brother Bertram who is unknown to the other Griffins. Stewie is voiced by Seth MacFarlane and speaks in an affected English accent.