It is false that Sodapop's real name is Keith on his birth certificte.
Sodapop Curtis's real name is not Keith on his birth certificate. In S.E. Hinton's novel "The Outsiders," Sodapop's birth name is actually Sodapop Patrick Curtis.
The nickname "Sodapop" reflects his easygoing and charismatic personality, and it is the name by which he is commonly known throughout the story.
As the book tells about the lives of the Curtis brothers, including Sodapop, Ponyboy, and Darry, there is no mention of his birth name being Keith. Sodapop's character is an essential part of the novel's exploration of friendship, family and social divides among the Greasers and the Socs making his true identity a crucial element of the narrative.