I mentioned this earlier to Astoria, but not all may have seen it there.

Astoria died of a blood curse that made her very weak when she gave birth to Scorpius. This curse was given to her family earlier in the linage by a vengeful muggle-born who had been treated terribly by her family. Not far from death, the witch that was tormented by Astoria's ancestor told her family that the blood curse would haunt her lineage until they have a set of generations who respect muggles and treat muggle-borns as equals. The younger of that generation must prove resentment for such cruelty in some way. As we know, Astoria and Scorpius do respect muggle-borns as equals and are not cruel to muggles. They are the set of generations that went against the blood purity bias. Scorpius, the younger generation, defied the group that was most discriminatory when after travelling time, he refused to let the world be run by Voldemort and the death eaters. When he fixed time, he also fixed and reversed his family's curse.