We know that babies who die go to heaven, see King David's son. But if they were born as sinners, how could they go to heaven then?
That is because we are not born as sinners like some people say.
The sin of Adam and Eve does not come upon people born in this world, for everybody will bear their own sin, and that is their sin, not our sin.
Adam and Eve were created knowing God, and it would of never entered their mind to eat of the tree of the knowledge of good and evil unless an outside source tempted them.
So God allowed Satan to tempt Eve and she sinned, and then Eve was the outside source that tempted Adam by showing him it was alright to eat of the fruit for she did not die physically.
When they ate of the tree they then had a choice between good and evil, and would have to make the choice to do what is right concerning the truth of God.
Since Adam and Eve's sin does not come upon people, babies are born innocent with no sin on their record.
And that is why the Bible says the angels always behold the face of the Father for the little ones, for they are protected spiritually while in the state of not being accountable for their actions when they are young, not having an understanding yet.
We are born innocent, but we are born not knowing God, so we will do wrong before we do right and come to God and repent of our sins.
Adam and Eve were created knowing God, and the sin of Adam and Eve does not come upon people so babies are born innocent with no sin on their record, but when Adam and Eve ate of the tree then they had a choice between good and evil, so all their offspring are born with a choice, so they are born not knowing God, so they will do wrong before they do right and make the choice to follow God and repent of their sins.
Being born in to this world without the knowledge of God, and having to make that choice later in life is what makes us sinners for we will do wrong before we do right coming to God.
So all have sinned and come short of the glory of God, but we are born innocent.
Which it is not our fault for being born with a choice, and without the knowledge of God, but there is no excuse for when we are older then we know to do right.