Is it permissible to give Zakat to a spendthrift brother, knowing that he will spend it on his children and his pleasures, and it is not possible to support his children directly?

It is permissible to give zakat to one's brother if he is poor or in debt and unable to repay, unless he incurred the debt for a sinful purpose, in which case he should not be given until his repentance is established, or if it is known that he will spend it on sinful acts. Mere extravagance and mismanagement do not prevent giving zakat to the poor.