if originated an iCloud account in 2013 wish is case sensitive how someome just change your from case senesitve email address to an noncase sensitive one especiall if your Apple ID is supposed to support Apple ID supported by iCloud.com@iCloud.com
I because it’s says for family sharing I would use icloud but is not on family sharing of any purchases or anything . I have only one family member that I know make that 2 that have an I phone and talk we will FaceTime sometimes that’s all.