Most cartoon characters never age, or if they do, they do super slowly. That's why it makes so much sense to cast adults whose voices have stopped changing (at least for a good few decades) to voice the characters. Even so, fans are surprised to learn that if the show did follow normal aging patterns, Peter Griffin would now be 60 years old!
This would, as the article points out, make Lois 58 and Stewie 20 years old. We've definitely seen older versions of these characters in certain episodes, but could you image if the show truly aged the characters in real time? It might even be more fun for some of the adults who've aged with the show, but Stewie as a baby is just too much fun to stop.
What do you think of the Griffin's actual ages? Do you think cartoons characters should age or not?