I'm not sure about cross-platforms functionalities (I only use it on my iMac and iPhone), so I can't really help you out with the first question.
Concerning your second request, Apple Music Family Membership was meant, obviously, for family, thus only the "In family" members can share it: up to 6 people can be part of this group, each with its own, separate Apple ID, but one credit card in common (from the family organizer), so all purchases are charged on that card (not only the subscription to Apple Music, but also iTunes Store, App Store and iBookstore purchases).
11-07-2016 01:08 PM