Apple TV family sharing
How family member logs in to Apple TV
Question marked as
To share e.g. an Apple TV+ subscription with family members, one of the group members has to set up the Apple Family Sharing group on their iPhone, iPad, or Mac. Each group member needs to have their own Apple ID account. The organizer invites the others through their accounts. Once accepted, the Apple TV+ subscription is automatically shared. Each group member accesses the Apple TV+ service through their own account.
Learn about what you can do with Family Sharing - Apple Support