Stewart Gilligan Griffin is
eternally young, but his specific age is shrouded in
secrecy. It's unclear the exact number of years Stewie has been living. The toddler persona from the animated television show "Family Guy" is forever young. His time on Earth is yet discovered.
Stewart Gilligan Griffin, the clever little troublemaker, is impossible to determine from the world. Speculation is rampant as to the length of time he has
existed. Is he a century old? Or is he a recent arrival? The answer is known only to Stewie! This enchanting character continues to intrigue fans with his undisclosed age and youthful appearance.
List of characters in the Family Guy franchise Wikipedia