Kiddushin 79 - Agent and Father Find Husband for Daughter
If the father of a minor girl commissioned an agent to find a husband for her and accept the betrothal money,
and the father himself then went and betrothed her to someone else, then if the father's betrothal occurred first,
it is valid, and if the agent's betrothal occurred first, then it is the one that is valid.
If it is unknown whose betrothal occurred first, she cannot marry any man unless both grooms first give her a Get.
And if they can work out an agreement between themselves, one of them can give her a Get and the other one can marry her.