Is it permissible to give zakat to a sister who is married to an unemployed man burdened with debts, and to a brother who does not pray, knowing that they are among the heirs? And does the saying "Zakat is not given to an heir" apply to them?

It is permissible to give zakat to a married sister if she is in need and her husband is poor. This is preferable as it combines charity and maintaining kinship ties. As for a brother who does not pray, if his abandonment of prayer is due to denial (of its obligation), then he is a disbeliever and should not be given zakat. However, if his abandonment is due to negligence or laziness, then he is a sinful Muslim, and it is permissible to give him zakat, and this is the more preponderant opinion. Regarding the issue of withholding zakat from an heir, this is based on the obligation of providing maintenance for relatives other than ascendants and descendants, which is a matter of scholarly disagreement.