^ Very true, something that Star Trek completely overlooks, because it's not expeditious for the stories. Anytime you travel such great distances, time moves much more slowly for you relative to people on Earth. When Picard made it back to Earth to visit his relatives after the Borg incident, his brother Robert would have been long dead! In truth, when Voyager returned home they would have been greeted by the great grand children of all the people they had known.
I think this was why Lost In Space had the premise of a whole family traveling together, because they'd never see each other again if separated. Candidate astronauts for real high speed space travel will either have very loose ties to family or travel with a loved one on board.