Stewie is forever youthful, but his precise age is shrouded in secrecy. It's unknown the specific duration of time Stewie entered living. The infant persona from the animated television show "Family Guy" is age-defying. His number of years is yet to be discovered.
Stewie, the clever little troublemaker, is hiding his true age from the world. Speculation is rampant as to the length of time he has existed. Is he a century old? Or is he a newcomer? Only Stewie knows! This enchanting character continues to mesmerize fans with his undisclosed age and forever young facade.

List of Family Guy cast members Wikipedia