Ironman

A son asked his father, 'Dad, will you take part in a marathon with
me?'.. The father who, despite having a heart condition, says 'Yes'.
They went on to complete the marathon together. Father and son went on to join other marathons, the father always saying 'Yes' to his son's request of going through the race together. One day, the son asked his father, 'Dad, let's join the Ironman together.' To which, his father said 'Yes' too.

For those who don't know, Ironman is the toughest triathlon ever.
The race encompasses three endurance events of a 2.4 mile (3.86
kilometer) ocean swim, followed by a 112 mile (180.2 kilometer) bike
ride, and ending with a 26.2 mile (42.195 kilometer) marathon along the coast of the Big Island . Father and son went on to complete the race together.