A few years ago, I wrote a book called Shadows in Flight. It was designed to be a half-length novel, so I couldn’t sprawl in my world creation and character development. The story followed a father with a genetic disorder that made him astonishingly intelligent and creative, but also afflicted him with gigantism that would, unchecked, eventually kill him.
Before the story began, he took off on a near-lightspeed voyage with those of his children who had the same disorder, in hopes that they could stay alive until somebody found a way to treat or cure the gigantism without losing the brainpower.
Along the way, they run across an ancient colony ship from an alien culture, one that had never reached its destination and now continued as an ecosystem without a purpose, since the colonists were
