I would like to introduce a little thought experiment we can have some interesting discussions about. Hopefully some fun too.
Imagine that life was a game, and the goal was to leave as big a 'genetic legacy' (i.e. the amount of your genes present in the next generation and their chances of being passed on to the generation after that) as possible. In a way this is actually the case, of course, but I don't think there are many people who consider this their primary motivation for building a career and having children.
But imagine this was your goal. What would be the best strategy? Anything goes, from 'spreading the seed' as wide as possible to focusing all your resources and hopes on one precious child. Bonus points are awarded for ensuring a good quality of life for your 'carriers'.