code: public Child addChildToFamily(final Family family, final Person person) {
          if (family == null || person == null) {
              return new Child();
          }
          final FamC famC = new FamC(person, "FAMC",
                  new ObjectId(family.getString()));
          final Child child = new Child(family, "Child",
                  new ObjectId(person.getString()));
          family.insert(child);
          person.insert(famC);
          return child;
      }
docs: Add a person as a child in a family.
  
  @param person the person
  @param family the family
  @return the Child object