At this time, family managers can only add children to Fitbit, not other parents or family members, even if they are part of the same Google family group.
This is a severe limitation. It means only one parent can see a child's stats, etc.
Moderator Edit: Clarified subject
Join us on the Community Forums!
Community Guidelines
Learn the Basics
Join the Community!
Not finding your answer on the Community Forums?
Go to the Help Site
Contact Support