His own sister, even if it's not true, it reflects poorly to have this kind of relationship with your sister that she'd say this, and if it's true, it's very problematic.
And for some reason, very very little mention of this. I just find it suspicious from a media behavior point of view.
The accusations are about events 25 years ago, when they were children. No one will ever be able to disprove this, so there's no way to undo the reputational damage.