public static Person HeadOfHousehold( this IQueryable<GroupMember> members )
{
return members
.OrderBy( m => m.GroupRole.Order )
.ThenBy( m => m.Person.Gender )
.ThenBy( m => m.Person.BirthYear )
.ThenBy( m => m.Person.BirthMonth )
.ThenBy( m => m.Person.BirthDay )
.Select( m => m.Person )
.FirstOrDefault();
}