Is it permissible to give zakat to the daughters of my husband's brother if their father is not in need but is so stingy with them that they wear old clothes?

A young child is considered wealthy by virtue of his father's wealth, so it is not permissible to give him zakat; because he is sufficed by his father's expenditure. However, if the children are unable to obtain sufficient support from their father due to his insolvency or refusal, then it is permissible to give them zakat; because in that case, they are considered poor and needy.