title: Rails 3. How to setup two instances of the same model in a belongs_to association?
body: <p>If I have a table called <code>enrollments</code> and this is my current basic enrollment setup:</p>
  
  <pre><code>class Enrollment &lt; ActiveRecord::Base      
    belongs_to :father
    belongs_to :mother
    belongs_to :child
  end
  
  class Father &lt; ActiveRecord::Base
    has_many :enrollments
    has_many :children
    validates :first_name, :presence =&gt; true
    validates :last_name, :presence =&gt; true
  end
  </code></pre>
  
  <p>Now I want to add a <code>guardian_1_id</code> and a <code>guardian_2_id</code> to the<code>enrollments</code> table. How would I set that up?</p>