Can't edit child account

When I go to "configure family" one of my children is missing now.  I don't know when this happened, Norton Family had been restricting his access (I hear the complaints) until recently.  When I then go to the "add child" screen to try to add him back, his accounts show on all 3 devices with a "/" in the box next to the account name and "(assigned to )"  Obviously, this should be "(assigned to childname)"   I obviously can't select those accounts since they are marked with "/" as already having been assigned to a child.  How can I recover and/or reset this child account?