Final answer:
Kin selection is a type of natural selection that favors the spread of alleles that increase reproduction by related individuals.
Step-by-step explanation:
Natural selection that favors the spread of alleles that increase reproduction by related individuals is known as kin selection. Kin selection is a type of natural selection that promotes the reproductive success of individuals who share genetic material with related individuals, even if it comes at a cost to the individual's own reproductive success.
For example, in some species of birds, individuals may forego reproducing themselves to help raise and protect the offspring of their close relatives, thereby increasing the spread of their shared alleles in future generations.