I want to write a science-fiction story concerning the rapid increase in technology affecting the speed at which spacecraft travel and passengers age (relative to each other). Theoretically, would it be possible that a son leaves a certain time (a number of years) before his father to travel to an exoplanet, then his father departs on a spacecraft that travels near light speed. Would his father age significantly less than his son, to the point where the son is older than his father. And if so, how far away would the planet have to be and how fast would the respective space craft need to travel? Thanks!