Kin selection is when you favor those who share your genes, and that we’re more likely to show altruism to relatives.
Take Vader for example. We find out in this scene that he’s Luke’s father. They are dueling it out and the much more powerful Vader could have blown him away, but evolution tells us that he would rather have him rule by him side by side. So he doesn’t kill him when he’s helpless. Luke gets away, but one movie later he’s back, and Vader decides he loves his genes too much to kill his son when his master tells him to, and instead throws Emperor Palpatine down the main shaft of the Death Star. That’s family love.
Why the sudden change of heart pops? says Luke. Well Luke, he’s really just selfish, and even though you’re a wiener, you’re his genes, and you’re worth more than a crusty old emperor. Kin selection in space.