It's one of the worst-kept secrets of family life that all parents have a preferred son or daughter and the rules for acknowledging it are the same everywhere: The favored kids recognize their status and keep quiet about it - the better to preserve the good thing they've got going and to keep their siblings off their back.
On the battlefield the military pledges to leave no soldier behind. As a nation let it be our pledge that when they return home we leave no veteran behind.