The moment Heero was appointed as the President of the Hero League. Heero had to immediately share his secret technique, the Ki Comprehension, and an eye technique that could differentiate a specter.
He did that but the Ki Comprehension he shared within the Hero League was not the same as his Ki Comprehension. It was a common Ki Comprehension in Dramonia.
For his Family, Heero would not let them learn the shared Ki Comprehension but the one that was better than the one he shared with the Hero League.
Of course, the one he shared with the Hero League was not an inferior secret technique. It was the best one among the common ones. But he had that much better than the one he shared and he wanted to share the better technique with his father-in-law and his grandpa-in-law.
