Under the close scrutiny of his ancestor and the other absolute powerhouses, Damian was forced to reveal every excruciating detail about how unpleasant his relationship was between him and his son.
In Damian's defense, he had many children of various ages, due to the fact that he himself was not that young, and his wife was a cultivator as well. The sense of familial bond was very limited between him and his children to begin with, and the fact that he ordered his children about like his subordinates, manipulating their relationship like it gave him control over them made them even more distant.
With his other children this was not much of a problem since none of them were absurdly talented, and even now had not come close to him in power. But Leon, his most talented son and Lex's father, was an entirely different case. He was always rebellious, though not to a problematic amount. It was only when he got to earth that the problem was exacerbated.