Peter and Lois have 2 sons:
Stewie Griffin (Seth MacFarlane) may be a baby, but he is as diabolical as the worst villain. He is highly intelligent, but he's still very attached to his teddy bear, Rupert.
Chris Griffin (Seth Green) is Peter and Lois' eldest son. He's not terribly bright, but he is a talented artist ("The Son Also Draws") and rock singer ("Saving Private Brian"). He admires his father and follows blindly into many of Peter's misadventures. Also, he fears the crazy monkey in his closet.
The Family Guy characters are what keeps the cartoon one of FOX's biggest hits. From the patriarch, Peter Griffin, down to a brainiac baby, and including their neighbors, the Family Guy characters are a funny bunch. Here is a list of Family Guy characters, with pictures and bios shared by Animatedtv.about.com.