Rose DeWitt Bukater and Jack Dawson were purely fictional characters. The was a Joseph Dawson who worked in the boiler rooms, but James Cameron was unaware of him at the time of filming.
Neither Rose or Jack actually existed, and were fictional characters created by James Cameron, though he did base old Rose on Beatrice Wood. He later discovered there was a J. Dawson on the ship but that was just coincidence it seems..
Thank God other people said it because I’m so tired of these videos depicting Jack and Rose as real people. I’ve seen 5-6 in my recommendations in the last couple weeks.