Because it's a cartoon.
Don't think too much about these kind of things.
Peter had it done. Chris considered it but wouldn't do it.
the episode when peter and Louis get Chris and Meg a boyfriend/girlfriend
Amanda Bynes played the voice of Anna (Chris' girlfriend) in the episode "Long John Peter".
The main characters in Family Guy are Peter, his wife Lois, children Chris, Meg, and Stewie, and dog Brian. Peter, Stewie, Brian, and Quagmire are all voiced by creator Seth MacFarlane.
There isn't an episode that features Peter and Glen in school together but you may be thinking about Season Five|Episode Eighteen Meet the Quagmires
no chris left behind
Peter gives Chris a bullfrog in the episode 'Long John Peter' (UK Season 8/US Season 7)
Peter had it done. Chris considered it but wouldn't do it.
gumble 2 gumble
Peter Griffin, his wife Lois, sons Stewie and Chris, daughter Megan, dog Brian.
Peter Orange was born in 1975.
syrup o Epicac
Trading Places
Peter and Chris use American Sign Language in the "Stewie, Chris & Brian's Excellent Adventure" episode of Family Guy. They learn ASL to communicate secretly when they travel to the future together.
Chris & Herbert sing "Friends and Lovers" by Carl Anderson and Gloria Loring
Chris Griffin, Louis and Peter's oldest child
Long John Peter