title: C# Family Class Design
body: <p>I am working on building a single family unit (class) for an application. I've done some searching and found solutions for entire family trees, but this app doesn't care about anything outside the single family unit which is defined as (Father, Mother, Child1, Child+n)</p>
  
  <p>This application is about the children (activities they can do based upon age and skill levels), but needs references to the parents.  The parents are only needed for reporting purposes and are required to have driver's license and insurance on file.  </p>
  
  <p>The application is being built using C# &amp; EF Code First.  None of the database annotation elements have been added to the class yet as that isn't the problem.</p>
  
  <p>Below are my classes.  The main business rule state that each sibling will have his/her own record, but they need to be linked together so only one mailing (electronic or snail) is sent, if the parents live together.  If the parents are divorced, then two letter (or emails) need to be sent.</p>
  
  <pre><code>public class Person
  {
      public int PersonId { get; set; }
      public string FirstName { get; set; }
      public string MiddleName { get; set; }
      public string LastName { get; set; }
      public string Suffix { get; set; }
      public string Sex { get; set; }
      public DateTime DOB { get; set; }
  }
  
  public class Youth : Person
  {
      public string CurrentGrade { get; set; }
      public Adult Mother { get; set; }
      public Adult Father { get; set; }
      public Adult ICE { get; set; }
  
      public virtual Adult Adult { get; set; }
  }
  
  public class Adult : Person
  {
      public string DriversLicense { get; set; }
      public string StateIssued { get; set; }        
      public string AutoInsuranceCarrier { get; set; }
      public string PolicyNumer { get; set; }
  
      public string MaritalStatus { get; set; }
  
      //foreign key
      public int VehicleId { get; set; }
      public virtual Vehicle Vehicle { get; set; }
  }
  
  public class Address
  {
      public int AddressId { get; set; }
      public int PersonId { get; set; }
  
      public string Address1 { get; set; }
      public string Address2 { get; set; }
      public string City { get; set; }
      public string State { get; set; }
      public string PostalCode { get; set; }
  
      public virtual Person Person { get; set; }
  }
  </code></pre>
  
  <p>The logic pattern I was stuck in was that siblings will have the same AddressId.  That failed when I applied the divorced parents, each having one child at their address. As far as mailings go, it would work because they are at different addresses. It doesn't feel like the best design.  If this were handled by UI, then it would work.</p>
  
  <p>My next thought was to create a Family class and add each family member to it.  In this instance, the user would have to make the selection of which people would be living at which address.</p>
  
  <pre><code>public class Family
  {
      public int FamilyId { get; set; }
      public int AddressId { get; set; }
      public List&lt;Person&gt; Person;
  }
  </code></pre>
  
  <p>That also doesn't seem like the best solution.  I feel there is a better design.  I just cannot find it on my own.</p>
  
  <p>Are there any pitfalls to one of these approaches that I'm not seeing yet?
  Can someone point me in a better direction?  And explain why that direction is better?</p>
  
  <p>Thanks in advance for all your insights!</p>