Is it permissible to give Zakat on wealth to one's father and married sister in light of difficult financial circumstances?

Scholars differ on the issue of giving zakat to parents. The preponderant opinion is that it is permissible to give zakat to the father if the son is unable to support him or pay off his debt. It is also permissible to give zakat to a sister if her husband's provision is insufficient for her and she is poor.