If he is in need, yes he can take as much as he needs from his miner children on whom he is the guardian. This is stated in the Qur’an 4:6. If he is not in need he should not take. As for adult children, again if he is in need they should give him and if they refuse he is permitted to take as much as he needs from their wealth even if it happens without their knowledge. This is of course in case they refuse to give him his normal satisfaction to his needs.