No, all online casinos frown at underaged gambling, this is because it ruins lives of people especially the little ones who can't develop a strategy to win or have a knowledge of planning, so they keep playing with all they have with the hope of winning.
If you find any online casino that accepts registration from children below 18, that casino is operating illegally and will be taken down if authorities gets to find out about that website, it's better you withdraw your funds and find another online casino.
If you find any online casino that accepts registration from children below 18, that casino is operating illegally and will be taken down if authorities gets to find out about that website, it's better you withdraw your funds and find another online casino.