Is it permissible to give Zakat to sisters who have no income, given that the mother receives a social security allowance that covers their living expenses and the daily household expenditures only?

It is permissible to give zakat (definition) to needy relatives, with the exception of ascendants and descendants whose maintenance is obligatory upon the zakat payer. Giving charity to needy brothers, sisters, and other relatives is both charity and maintaining kinship ties, as the Prophet, peace and blessings be upon him, said to Abu Talha: "I think you should give it to your closest relatives." It is permissible to give zakat to needy sisters, but it is not permissible to give it to a needy mother if she is the zakat payer's mother, or his paternal grandmother if his father is alive and her maintenance is obligatory upon him.