Son+older+than+father

Because time moves slower as you travel closer to light speed, it is possible for a son to be older than his father. If the father goes on a space trip for 5 years. Because he is traveling at a faster speed then his son, time moves slower for him than his son on earth. Now his son will age at a faster rate than he does, making it possible for the son to be older than the father. You can find it out how much someone will age in a certain situation using the time dilation equation.