Strictly speaking, it must give the _gene_ a reproductive advantage, not necessarily the animal. Often, these two advantages are aligned. But they need not be. This is the case in kin altruism. And this is also, why "promoting longevity beyond the reproductive stage of one's life cycle" affords sometimes very much such benefits. Example: grandparents can help raising their children's children (and their children's children's children ;)). Kin altruism becomes even more apparent in ants (or other social animals). Worker ants or bees are pretty much infertile but they help a lot.
It should be noted that the difference is much more extreme for ants than it can be for mammals due to a genetic quirk where a female ant shares 50% of her genes with her children and 75% with her sisters. (Therefore having more sisters is better than having children.)
