Not necessarily; natural selection favors a species that reproduces, but that does not mean every member of the species must reproduce. For example, it could be favorable to have a small number of individuals who have more offspring than they can care for on their own, but whose siblings/extended family assist with raising those children (this is more or less how a wolf pack is organized). In the end what evolution is about are genetic traits, and someone who helps raise nieces/nephews/cousins is helping to propagate their own genetic material.
betterunix2|4 years ago