This concept is categorized under altruistic behavior, where one’s own fitness is reduced while others’ are increased, which is formally known as inclusive fitness. Behind this idea is the sharing of genes between relatives, and by unselfishly protecting and caring for relatives, one’s own genes are kept alive and passed down via their relatives.
An example of kin selection is shown in honey bees, whose haplodiplontic lifecycle allows different degrees of relatedness amongst the population. Hence, although they generally protect and care for each other, the worker bees tend to assist their sisters more than their brother drones.
Another example is seen in jackals. When the wild dogs mature, they are ready to leave their family, but often times their parents use their teeth and gently bite the mature child’s neck area to keep them in the family as a babysitter for the next generation of pups.