GetPeople.rb

class Customer < ActiveRecord::Base
  has_many :groups
end

class Group < ActiveRecord::Base
  belongs_to :customer
  has_many :members
  has_many :people, :through => :members
end

class Member < ActiveRecord::Base
  belongs_to :group
  belongs_to :person
end

class Person < ActiveRecord::Base
  has_many :members
  has_many :groups, :through => :members
end