Create & manage a shared YouTube TV membership, or family group

If the family manager with a YouTube TV membership has invited you to join the family group, you’ll get an email invitation. Follow the instructions in the invitation to join the family group. To join a family group, you must be 13 or older, and have a Google Account. You can access your own library, recordings, and personalized recommendations.

 https://support.google.com/youtubetv/answer/7251139?hl=en