Sorry that this reply is late in coming. Had a busy schedule elsewhere.
Are you not aware of "Original Sin"?
The "Sin" that was passed to all mankind in Adam?
The reason why the Scriptures say: That all children come from the womb lying?
When Adam sinned, he stood for the whole of the human race. His sin was upon us and we all died in him.
Rom 5:12 Therefore, as through one man sin entered into the world, and death through sin; and so death passed unto all men, for that all sinned:--
This "Original Sin" brought upon us all - death and this has nothing to do with individual sin. We all fell in Adam.
Rom 5:13 for until the law sin was in the world: but sin is not imputed when there is no law.
Rom 5:14a Nevertheless death reigned from Adam until Moses, even over them that had not sinned after the likeness of Adam's transgression...
Rom 5:18a So then as through one trespass the judgment came unto all men to condemnation...
Original Sin is often not taught in the churches today because it is an unpopular subject. However, to understand and truly appreciate God's saving grace, we must first clearly understand the power of the "sin nature", which befell us all and all of creation.
Therefore, any attempt to try to explain away mankind's guilt and condemnation before the Lord is vain. Adam was humanities head and anything he would do or not do, we all would do or not do in the same likeness. Not a single one of us, was, is or will be, better than Adam. Therefore, God is Just in bringing down Condemnation upon us all.
As believers, we must learn to except Biblical Truth and not allow our feelings or emotions to carry us off into error. This is far more difficult for those who have gone through child loss or are presently caring for a child that has mental deficiencies. However, never underestimate, in the case of mental defects, what God can do in His saving Grace.