User Relationships | drupal.org

Allows users to create named relationships between each other. It is the basic building block for a social networking site, or any site where users are aware of one another, and communicate.

There are many features on offer. It'd be worth your while to check it out.

Admins create relationship types (friend, coworker, etc). Relationship types can be setup to be one-way or mutual. If a relationship type is one-way (subscriber) only the requester is shown as relating to the requestee. Relationship types can also be set as needing or not needing approval.

Admins can give users the option to auto approve relationships on a per-relationship type basis.

Also bundled with the core relationships module is a set of eight ten other modules directly related:

1. User Relationship Mailer will (conditionally) send email notifications regarding relationship creation/removal/approval/disapproval/cancellation.
2. User Relationship Defaults creates default relationships to any user joining the site (think Tom on MySpace).
3. User Relationship Implications allows admins to specify implied relationships (Manager implies Coworker) that are automatically created when this implying relationship is created and removed accordingly.
4. User Relationship Blocks blocks that may be useful.
5. User Relationship Invites (5., 6.x new!) requires the Invite module and allows users to specify a relationship to a user that they invite to join the site.
6. User Relationship Views (5.x; 6.x) integration with the views module providing filters, arguments, and fields.
7. User Relationship Privatemsg (5.x only) integration with the privatemsg module showing your relationships in the quick select list.
8. User Relationship Migrate (5.x only) allows admins to migrate Buddy List relationships to User Relationships.
9. User Relationship Elaborations (6.x only, for now) lets users send a message with their relationship request to another user.
   1. User Relationship Node Access (6.x, 5.x-dev) lets users control access to their content based on relationships