I too don't feel having a partner and a family is enough for me to consider life fulfilling. For me a more meaningful life would also include doing more programming - but on a projects that I believe in, instead of ones I get assigned by my employers. It would also include a lot of what you'd call hard work in other domains, like electronics, chemistry, etc. - but again, self-directed, and for things that I care about.

Basically, I have shit ton of projects, ideas how to improve things for myself and people around me, that I don't have time to pursue because of $dayjob and $obligations. And I guess one could summarize it with one word - autonomy. This is something that I think leads to a more fulfilling life.