Is the waiver of retribution by the drug-addicted brother valid, and is it permissible for the remaining heirs to retract this waiver and demand retribution from the killer, especially since the agreed-upon amount was not paid on the specified date?

Justice or maturity is not a condition for the validity of pardoning retaliation (Qisas); rather, maturity and sanity are conditions. Therefore, the pardon of a minor or an insane person is not valid. The pardon of a drunkard or a drug addict is valid if he is in full possession of his faculties. Retaliation (Qisas) is waived if one of the blood relatives pardons or settles for compensation, and the heirs cannot retract their brother's waiver. The money settled upon is not exclusively for the addict; rather, the rest of the blood relatives share in it according to their shares. As for the killer's failure to pay the money, it is up to the judge. Retaliation (Qisas) is waived if one of the blood relatives admits to reconciliation and pardon for a sum of money, even if the killer denies that reconciliation took place, due to the establishment of doubt, and it transfers to blood money (Diyya).