[ID]: integer
[FirstName]: TEXT
[LastName]: TEXT
[Father]: INTEGER
[Mother]: INTEGER

class Person{
public string FirstName{get;set;}
public string LastName{get;set;}
public Person Father{get;set;}
public Person Mother{get;set;}
public IList<Person> Childrens{get;set;}

class Person{
private int id;
private IList<Person> _childrens1 = new List<Person>();
private IList<Person> _childrens2 = new List<Person>();
public string FirstName{ get; set;}
public string LastName{ get; set;}
public byte Gender { get; set; }
public virtual Person Father{ get; set;}
public virtual Person Mother{ get; set;}
public virtual IList<Person> Childrens
{
   get
   {
      List<Person> ret= new List<Person>( _childrens1 );
      ret.AddRange( _childrens2 );
      return ret;
   }
   protected set { }
}

public virtual IList<Person> Childrens1
{
   get { return _childrens1; }
   protected set { _childrens1 = value; }
}

public virtual IList<Person> Childrens2
{
   get { return _childrens2; }
   protected set { _childrens2 = value; }
}
public virtual void AddChildren(Person child)
{
   if (Gender == Male)
   {
      if (child.Father != null)
      {
         child.Father._childrens1.Remove( child );
      }
      child.Father = this;
      _childrens1.Add(child);
   }
   if (Gender == Female)
   {
      if (child.Mother != null)
      {
         child.Mother._childrens2.Remove(child);
      }
      child.Mother = this;
      _childrens2.Add(child);
   }
   
}
const byte Male = (byte)'M';
const byte Female = (byte)'F';
}

<class name="Person" table="Person" lazy="false">
   <id name="id" unsaved-value="0" column="ID" type="System.Int32" access="field">
      <generator class="identity" />
   </id>

   <property name="FirstName" column="FirstName"/>
   <property name="LastName" column="LastName"/>
   
   <bag name="Childrens1" fetch="select" inverse="true">
      <key column="Father"/>
      <one-to-many class="Person" not-found="ignore"/>
   </bag>
   <many-to-one name="Father" fetch="select" column="Father" class="Person" not-found="ignore"/>

   <bag name="Childrens2" fetch="select" inverse="true">
      <key column="Mother"/>
      <one-to-many class="Person" not-found="ignore"/>
   </bag>
   <many-to-one name="Mother" fetch="select" column="Mother" class="Person" not-found="ignore"/>
</class>

public enum Gender
{
  Male,
  Female
}

public class Person
{
  string firstName;
  string lastName;
  Person mother;
  Person father;
  List<Person> children;
  Gender gender;
}