Adding existing Apple ID to Family Sharing
My son received an iPhone from his Aunt who set it up with a gmail address as his Apple ID instead of the iCloud Apple ID that I already have for him in Family Sharing. Now I’m trying to add this new gmail Apple ID to Family Sharing. The only instructions I can find to add a child to FS asks questions as if I’m adding a completely new ID. How do I add an existing Apple ID to FS?