A broker has an opportunity to take a listing that has been in the family for years and the broker still owns a part of the property with the family. The broker

Agency by estoppel arises when a principal's actions lead a third party to reasonably believe that an agency relationship exists, but it does not apply here. The broker has a vested interest in the property, which means they are not simply an outsider and need not refuse the listing.

Negotiating a single agency would limit the options for collaboration and is not necessary given the broker's ownership interest. The broker can still work with other parties, provided full disclosure is made regarding their ownership, thus allowing for a more flexible and inclusive representation.

Agency by ratification occurs when a principal approves an action after it has been taken, which is not applicable here. The broker already has an established interest and does not need to wait for ratification from the other owners to represent them, as they can proactively disclose their interest and proceed with the listing.