Does the marriage become void if the father marries off his daughter as a virgin, while she is a Thayyib (previously married), and he is unaware of that? Is she obliged to inform him before the marriage contract? And does the marriage become unlawful due to the difference in rulings between a Thayyib and a virgin? What is this difference?

The father's marriage of his non-virgin daughter as if she were a virgin does not affect the validity of the marriage, whether the husband stipulated virginity or not, and whether the father knew of the loss of virginity or was ignorant of it.

The woman is not obliged to inform the suitor about the loss of her virginity, unless he stipulated it. In that case, it is not permissible to conceal the matter from him, but she is not obliged to inform him of the reason for its loss.

This does not affect the fundamental validity of the marriage. However, if the husband learns that she is contrary to what he stipulated, he has the option.