iOS 18 doesn't have option to add Parent/Guardian to Family Sharing

I am trying to set up an account for my child in our Family Sharing plan. To do this, I need to be a Parent/Guardian role. The organizer of the family (not me) tried to change my role from "Adult" to "Parent/Guardian", but there is no option to do so. She also tried removing me and adding me back, but there is no option at any point when adding someone to designate them as a "Parent/Guardian". I do not want to have to rely on her to create the child account and manage purchases/permissions. This seems like a bug in iOS 18 and I cannot find relevant help anywhere online.