Is it permissible for a man to marry the daughter of a woman he had married through an 'urfi (customary) marriage, and then it became clear that his marriage to her was void, and both repented to Allah?

An 'urfi marriage (customary marriage) is either valid, void, or constituteszina. In all cases, if consummation occurred, it is not permissible for the husband to marry the daughter of the woman he married.

If the marriage was valid, then the daughter is his stepdaughter and is unlawful for him. If it was void or فاسد (defective, e.g., without a guardian or witnesses), she is likewise unlawful for him, because sexual intercourse under misconception (shubha) prohibits marriage due to affinity, just as lawful intercourse does, by scholarly consensus. If it was a case of zina, then the daughter of the woman with whom zina was committed is unlawful for the perpetrator according to the Hanafis and Hanbalis.