What are the eight categories for the distribution of Zakat, and is it permissible to give it to the wife's relatives, such as a needy mother-in-law, or is it restricted to the husband's relatives, and is it permissible to give it to a brother who is capable of working but unemployed and has a family?

The eight categories of people entitled to Zakat (definition) are those whom Allah mentioned in His saying: "Indeed, [prescribed] charitable donations are only to be given to the poor and the needy, and to those who work on [administering] it, and to those whose hearts are to be reconciled, and to [free] those in bondage, and to the debt-ridden, and for the cause of God, and to the wayfarer."

Zakat is preferably given to a poor relative, unless a distant person is in greater need. "Relative" here includes a person's kin from the father's and mother's sides, such as brothers and sisters (unless their maintenance is obligatory), and paternal uncles and aunts, and maternal uncles and aunts.

As for in-laws, they are not blood relatives, but in-laws are more deserving than others by virtue of the marital relationship. Giving Zakat to the poor mother-in-law is permissible, as is giving it to a brother who is eligible for Zakat, even if he is able to earn a living.