BuddyPress.org

You can also limit the maximum number of friends.

You can use specially designed WordPress theme, I think the solution already exist.

BuddyPress
BuddyPress is a powerful WordPress plugin that takes the self-hosted WordPress sites to integrate with social network and community features. It allows you to handle user profiles, user groups, activities, and others within WordPress blogs. So you can use it as a social network for schools, colleges or universities or a communication…[Read more]

@shemakeswebsites just change the group page slug from groups to regional-groups