# пользователь
class User < ActiveRecord::Base
has_many :bosses, through: :boss_assistants, :source => :user
has_many :assistans, through: :boss_assistants, :source => :user
end
# связь
class BossAssistant < ActiveRecord::Base
belongs_to :boss, :class_name => 'User', :foreign_key => 'boss_id'
belongs_to :assistant, :class_name => 'User', :foreign_key => 'assistant_id'
end