Once a Member has joined an organization, only an organization owner can remove them. 

When you remove a Member from the organization, all family shares associated with that Member are removed (if the organization is set to use the User-to-User share option). This means for any families the Member owned, they retain ownership and other members of the organization will no longer be able to access those families. For any families shared with the Member by other members of the organization, the Member who has been removed will no longer be able to access those shared families.

To remove a member from your Organization (if you are the owner):

  1.  Go to Account > Organization Settings
  2. Click on the Members tab
  3. Click the Remove button and confirm removal