Aside from seducing, impregnating, then killing Gwen Stacy — Green Goblin goes the extra effort of douchebaggery by raising their twins with a revised story of what happened to their mother. Putting all the blame on Spider-man for her death, he trained the two kids for his ultimate revenge on Spider-man. Gabriel would later on assume the alias of the Gray Goblin.
From – Amazing Spider-man Vol. 1 #514