What is the ruling if two sons kill one parent each, but the parents were not married to each other?
Chapter on Distant Kindred (Dhawu al-Arham)
Al-Mughni
Book of Inheritance Shares (Farā'id)
Primary text
If each son kills one of the two parents, and the parents were not spouses, each son is entitled to Qisas against his brother. However, neither can execute Qisas without invalidating the other's right to Qisas, resulting in the mutual waiving of Qisas.
Supporting text
If one brother forgives the other, the remaining brother may execute Qisas against the forgiver and inherits from him according to the apparent position of the Madhhab. If one brother rushes to kill the other brother first, Qisas against him is waived, and he inherits from the deceased according to the apparent position of the Madhhab. An alternative opinion suggests that he should not inherit from the killed brother, and Qisas should be obligatory against him for the killing, because when the two rights to Qisas become equal and combining the execution of both is impossible, they both lapse, leaving no legal standing for them. Thus, the one executing Qisas is considered an aggressor in his execution and should not inherit, and Qisas is obligatory against him for the killing.