Jesus said we must be as little children to enter the kingdom of Heaven, so obviously the little ones are innocent and not tainted by sin. Why wouldn't they go to Heaven? Little children who are too young to discern the difference between right and wrong are innocent in God's eyes, regardless of their parents spiritual status. There is a verse in the OT that a son does not inherit the sins of his father. To say at what age a child becomes knowledgeable enough and responsible for his/her sins is purely speculative -- I think it varies by the individual.
Do you believe all humans, when born, have an entitlement to Heaven?
SD
I would respectfully disagree with you, my FRiend. The Scriptures say that "ALL have sinned and fall short of the glory of God." All includes newborn babies.
If God chooses to save newborns, that's up to Him. If not, that's also up to Him.
Actually, we are tainted by sin at birth. It's original sin and we inherited it courtesy of Adam and Eve. It is completely by God's grace that we are redeemed; Jesus purchased us that redemption, but we did nothing to deserve it.