It is truly sad to read this story. I pray that children will be able to move on and overcome their painful ordeals. May God give them the strength to lead their lives free from nightmares and most of all, self-doubt. I hope that they will be able to fully understand that none of this was their fault.
As for the "father", someone is trying to excuse his heinous acts with the assumption that he may have been abused in his youth. As terrible as that is, it does not mean that he did not know that what he was doing was wrong, that he no longer had the free will to decide and understand what is right and what is wrong. He made the CHOICE to do the wrong thing and has justly been punished for it.
Again, my sympathies for the victims. You are strong ! You were angels that have been violated, but you are still angels !