Is the consent of the Kitābī (People of the Book) wife's son to the marriage sufficient for the عقد (marriage contract) to be valid, without his physical presence? And is it permissible for her son to be her guardian instead of her paternal uncle? And is the contract valid if the son later consents to the marriage?

A marriage contract with a Muslim woman or a Kitabiyyah (woman of thecripture) has conditions and pillars without which it is invalid, such as the guardian, witnesses, offer, and acceptance. The one who undertakes the marriage of a Kitabiyyah is her guardian, who shares her religion. The guardian's consent alone is not enough; rather, he must conduct the contract himself or appoint someone to do so. If the contract is concluded without the direct involvement of the Kitabiyyah woman's guardian or his agent, the contract is invalid and must be rectified by conducting a new, legitimate contract, unless validated by a judge who does not require the guardian.