Change or add an adult organizer

I have a 9 year old son who got the IPhone XR as a birthday gift last month and his aunt that bought it for him set up the family sharing and the find my device or location sharing.I have a phone plan with 3 lines which 1 of those lines was my sons line that i have had on for him over a year with a different type of phone so the gift iPhone was switched out n the place of the phone he had already.I am the one who pays the phone bill monthly and he is my son so I am the one who should be the organizer and have control over the iPhone but as the someone else is the organizer and I do not know that person’s information to remove it nor can I locate my sons aunt to ask the info to be able to change that my question is if there is anyway I can add myself as another organizer or delete her as the organizer and add myself n the place of her to control my sons phone which I pay the bill on monthly.