title: Prolog family tree : check if two persons are from the same family
body: <p>I can check people relationships (uncle, aunt, father, grandfather...) in a tree but now I'd like to know if two people are in the same or a different tree i.e. check if they are from the same 'family'.</p>
  
  <p>The definition of a 'family' is kind of stupid because we all have a common ancestor but that's the exercise I have to do...</p>
  
  <p><a href="https://i.stack.imgur.com/6OvUn.png" rel="nofollow noreferrer">Family tree example</a></p>
  
  <p>I'd like to check that Maurice and Floriane are from the same family...</p>