Easy enough - On your Group Leader Site, scroll down to the Group Options section and click on "Manage Group members and titles".
|Group Leader Site - Group Options|
|Modify Group - Leader status, ior click 'X' to remove family from Group|
Group Members can also remove themselves from a Group by clicking on "Edit My Information" on their Member Signup Sheet, click on the 'Groups' tab, and click the 'X' next to the group from which they want to be removed.
|Edit My Information - Group Tab|