>>John, have you tried Kindle Family Library? You can share books easily that way
So it says... but did you try it? Family profiles are sub-profiles under yours and aren't real accounts so kids lose access to books they've bought on their own account, plus now they need your assistance and/or passwords to get new books. Apple's version that links actual accounts of family members, is better.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1