I think Jack is Pisces and Ross is Scorpio.
Analysis of Jack:
Jack is a painter with rich artistic elements. One bad thing is that he likes gambling. But it was that time that he won the ticket for the Titanic that day. So he was lucky to meet rose. When the ship sank, he sacrificed himself to let Ross climb to the cover of a lifeboat floating on the sea, while he was immersed in ice water.
As we all know, Pisces is a very artistic constellation, addicted to gambling and with the spirit of self-sacrifice.
Analyze rose:
Ross is very beautiful, which made Jack immediately attracted to her and drew her. Rose knew that she didn't like her fiance, but she was forced to marry her. It made her want to kill herself. Later, after she got along with Jack, she had a good impression on each other. Even in the face of sudden disaster, she had to leave her fiance decisively. When Jack froze to death, she still kept her promise to Jack, that is, to live well.
Scorpio is like this, with clear love and hate and firm will. Scorpio people have an attractive charm.
Also, because they are both water signs, Pisces and Scorpio are an ideal couple.
I wonder what you think of my guess? Haha ~ ~