the 2 main characters,Jack and Rose were not real passengers on the real titanic ship in 1912,but they did interact with real people who were actual passengers from the real ship(i.e Thomas Andrews,Molly Brown,John Jacob Astor and others).Does that answer your question?
In 1912 there wasn't a real Rose o Jack. They're fictional characters. Gloria Stewart was never on the ship then, she was born in 1910 which makes her 2 years old. There is several historical characters that were actually on the ship like Captain Smith, Thomas Andrews, Bruce Ismay, Margret "Molly" Brown, Officer Murdoch and the many others.