Is it permissible for a married man to marry a divorced woman who is an orphan, having no guardian except her paternal aunt's sons, whom she refuses to marry, if this takes place before a lawyer, with the presence of two just witnesses, and with offer and acceptance?

The guardian (wali) is a condition for the validity of marriage according to the most preponderant opinions of the jurists. Thus, a woman may not marry herself off, nor may another person marry her off without the permission of her guardian. If a marriage takes place without a guardian, it is invalid.

The sons of the paternal aunt are not among the 'asabah (agnates/male relatives on the father's side), so they have no right to marry off the woman, nor do they have the right to marry her without her consent.

If a woman has no guardian, then her guardian is the Muslim ruler (Sultan) or whoever takes his place in Western countries, such as Islamic centers.

It is not a condition for the validity of marrying a second wife that the first wife knows or consents. However, the husband must be just among his wives.