Is it permissible to give zakat to needy siblings, among them a university student, a simple laborer, and a sister married with barely enough to live on?

It is permissible for a person to give from Zakat to his brothers and sisters if he is not responsible for their financial support. However, it is not permissible for him to give from his Zakat to his father, mother, or children, because he is obligated to support them financially.