If we're talking unfortunate families, I'm pretty sure without looking it up that Jodie Foster has a bitter, unsuccessful younger (?) brother who's tried his best to scrape a living over the years by hawking stories about her to the tabloids.
I was going to suggest that being someone like Carl Hoddle would be a pretty crap deal, playing a sport in which you will forever be compared unfavourably to your considerably more talented brother (Glenn, obviously), but on googling him, it turns out he died earlier this year, so perhaps there are better examples about.