I am trying to set family sharing. When I push the Set Up Family button I am told my account is already used for family sharing and to ask [myself] to send an invitation for sharing. I don't have any other device which allows me sending such invitations or reset the family sharing. I set up the original account on a PC that has been decommissioned. How can I get control of my 'family sharing' function?
MacBook
Pro, OS X Yosemite (10.10.5)