This scenario is one of :
B. Kin selection.
Explanation:
In Evolutionary Psychology, the concept of Kin selection is an important one in terms of Darwinism study and the study of shared genetics.
It basically means that the people of the same kin are predisposed to each other by their genetics that are common.
This would mean that there is a higher chance of successful organ donation inside the kin than outside because the bodies of the people are familiar in terms of their genetic make up.