To enable Multiple Relationship Groups, which is a feature that allows users to add individuals to more than one group or household, the Admin needs to use Custom Settings. Custom Settingsare similar to custom objects and enable application developers to create custom sets of data, as well as create and associate custom data for an organization, profile, or specific user. The Admin can use Custom Settings to enable Multiple Relationship Groups by following these steps:

From Setup, enter Custom Settings in the Quick Find box, then select Custom Settings.

Click Manage next to Group Member Record Type Mapper.

Click Edit next to Default Organization Level Value.

In Multiple Relationship GroupsEnabled, select True.

Click Save.