Basically

Damien and Pip are from a movie series and novel called " the omen " and " great expectations "

Damiens movie got made into a novel , Pips novel got made into a few movies over the centuries

Damien's life is based in the 1960s , Pips life is based in the 1800s

Damien is the antichrist so he was born in hell from Lucifer and a Jackel

Pip and Damien got put into Southpark , Damien leaving after his debut episode probably due to copyright stuff with him based on the omen movies , Damien only making small appearances in the background of some episodes , being forgotten mainly