My wife and I have separate Apple IDs. To simplify (!) things a while ago we both started using a third ID.
Now with Family Sharing we can each access the other's purchases.
So I set myself up as the family organizer, invited Laura, and invited the 3rd account.
Well to accept the invitation for the third account, I would have to sign out of iCloud, loosing a bunch of data, or possibly having merge problems later.
The invitation has to be opened in Mail. I try not to use Mail. I certainly didn't want to not only sign out of iCloud, but also configure yet another account on Mail. (The third Apple ID forwards to both of us.)
What to do?
Best Answer
.The answer turned out to be only slightly convoluted.
With luck this may help other people in similar circumstances.