The only visible ancestors we have before the canon epilogue are Augusta Longbottom, and, by the end of the series, Andromeda Tonks.
Not only that, but if I remember correctly, Augusta Longbottom was portrayed as being considered old. Wizards seem to follow the same schedule as muggles for settling down and having kids, so she should have been about 70 when Nevil started at Hogwarts - not even middle-aged compared to a 200-year expected lifespan.
I'm not sure this is too unusual relative to our own society: these days life expectancy in Western countries is around 80-100, but people still tend to be considered to be getting old at fifty, relatively old by sixty and definitely old by seventy. In our case though we have the excuse that it's a recent change.
This implies pretty awful things about wizarding society, if we can safely assume that people with children retire around sixty and then spend the next century or so being ornamental, and that it's been like that for centuries.
[Update: and now there's a fifth discussion thread, which you should probably use in preference to this one. Later update: and a sixth -- in the discussion section, which is where these threads are living for now on. Also: tag for HP threads in the main section, and tag for HP threads in the discussion section.]
The third discussion thread is above 500 comments now, just like the others, so it's time for a new one. Predecessors: one, two, three. For anyone who's been on Mars and doesn't know what this is about: it's Eliezer's remarkable Harry Potter fanfic.
Spoiler warning and helpful suggestion (copied from those in the earlier threads):
Spoiler Warning: this thread contains unrot13'd spoilers for Harry Potter and the Methods of Rationality up to the current chapter and for the original Harry Potter series. Please continue to use rot13 for spoilers to other works of fiction, or if you have insider knowledge of future chapters of Harry Potter and the Methods of Rationality.
A suggestion: mention at the top of your comment which chapter you're commenting on, or what chapter you're up to, so that people can understand the context of your comment even after more chapters have been posted. This can also help people avoid reading spoilers for a new chapter before they realize that there is a new chapter.