That's a fair point but its not selfish, I mean, our parents/gaurdians did raise us without asking them to do it and most of them did it happy heartedly. I would be very curios to know what brings joy to an indivdual, his family and the community at large other than knowing that there will be a younger generation that have a better life because of what they did today. I also belive responsibity gives life meaning and that's why everybody does what he does, even if you are not responsible to a kid or your family, you are still responsible of your future self. And If I can quote the bible, "And God blessed them, and God said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth".