Google family calendars are now rolling out to users

If you’ve taken advantage of the new Family Group feature from Google, one of the things included is a new family calendar. All members of the family group will automatically be looped into the calendar. Those in the group can add and modify events and rename the calendar. Non-family members can’t be added into the calendar. Calendar sharing has always been available for Google Calendar but this feature will avoid duplicate calendar events for those in the group. It’s not yet live for all users but it should be showing up soon.

Source: Android Police