What is the nature of the prohibition of marrying the daughter of one's wife after the marital relationship with her mother has ended, and what is meant by "al-hujoor" in the noble verse?

The daughter of a man's wife with whom he has consummated the marriage is forbidden to him, as are her daughters' daughters and her sons' daughters, however far removed in descent. This is due to affinity (marriage relationship). Allah Almighty says: "And your step-daughters under your guardianship, born of your wives to whom you have gone in. But if you have not gone in unto them, there is no sin upon you" (An-Nisa: 23). The phrase "under your guardianship" is a description to indicate the prevalent situation, not a restrictive condition.