Could be the same situation as Worf, a refugee. Klingons war with everyone. You gotta figure they’ve left a few orphans around. But it falls under a been there, done that category. Then I was thinking a life-debt with Mal but then Mal IS Han Solo. So I don’t like that either.
In the episode where Worf and Dax get married. When Dax is asked to recite the history of the House of Martok, Dax gleefully reveals her discovery that Sirella has no imperial blood, and is in fact descended from a concubine. Naturally, Sirella is infuriated. Perhaps Zoe worked in the archives and found many discrepancies. She felt her people had strayed from once honorable days. She longed to find a fight worth fighting. She found the Marquis.