Are one's brothers and sisters eligible for zakat, and is it permissible to give it to them, or should it be given to those who are deserving?

The estate left by the mother is an inheritance that must be divided lawfully among all her heirs according to their prescribed shares, and no one is permitted to prevent its division. It is not permissible to compel any of the heirs to a specific method of division mentioned by the mother, for Allah Himself has taken charge of dividing the inheritance and clarifying the shares in His Book. Allah the Almighty says: "These are the limits [set by] Allah, and whoever obeys Allah and His Messenger will be admitted by Him to gardens beneath which rivers flow, abiding eternally therein; and that is the great attainment. But whoever disobeys Allah and His Messenger and transgresses His limits - He will admit him to Fire, abiding eternally therein; and he will have a humiliating punishment." The Prophet, peace and blessings be upon him, said: "Indeed, Allah has given every rightful person his right, so there is no will for an heir."

As for the brothers taking from zakat, if they are wealthy due to what they own from the inheritance, then it is not permissible for them to take from zakat.