What is the ruling on marrying a second wife secretly without her guardian's consent, in order to preserve the first family from disintegration and to avoid fornication?

The guardian (wali) is a condition for the validity of the marriage according to the most preponderant opinion among jurists, which is the view of the majority. Therefore, it is not permissible to marry a woman without the permission of her guardian. If it occurs without the guardian's permission, the marriage is void. However, if it is with the guardian's permission and the presence of witnesses, it is a valid marriage, and its concealment from the general public does not make it a secret marriage prohibited by Islamic law. In the case of polygyny, the husband must be just between his wives regarding lodging and expenditure. If one of them voluntarily waives her right, there is no harm. The wife must obey her husband in what is good and permissible, and this includes responding to his call to the marital bed; otherwise, she would be considered disobedient (nashizah).