Is retaliation obligatory if a maternal uncle kills a nephew, and the nephew's mother inherits the right to Qisas, subsequently dying and the right transferring to her son?

Primary text

If a maternal uncle kills his nephew, and the nephew's mother inherits the right to Qisas (or a portion thereof), and subsequently the mother dies due to being killed by her husband or another party, and her son inherits the right from her, the right to Qisas is extinguished. This is because a prior impediment invalidates a subsequent right transfer. The liability shifts to Diyah (blood money).