iCloud is a service that keeps one user's devices and computers in sync. It is generally not intended as a storage medium where other users can access data. Of course multiple users can use the same icloud account, but then, they will be sharing contacts, emails, reminders, notes, etc. But that's usually not what users want to do.
As for photos, there are shared photo streams; do a google search on this for mor info. Music? No, you can 't share unless the family uses the same Apple ID for the iTunes store, which is not the same thing as an icloud account.