That doesn't matter if it's inherited patrillinially. For example, the Y-chromosome is only inherited through the father, and mitochondrial DNA is only inherited through the mother. It's not about being a descendant- it's about patrilinnial inheritance. For example if Joseph was Jesus' real dad, Jesus could not be king or messiah, because Joseph's line was part of Jaconiah's line which was cursed from being king.
Right, the pharisees would not admit that they were blind (sinners) and needed to be healed.
He was saying they needed to become like children with respect to their faith. Children like to learn new things, but the pharisees thought they knew it all already. He wasn't saying the children were sinless.
Being aware of sin validates the sin. The reason Jesus spoke to the crowds in parables was a bit like a mercy. To some extent it's better to not make someone aware of their sin if they'll just reject the gospel after having received the truth; there comes greater condemnation with that. See Matthew 13:13-17, John 9:41, and more.
The Bible preaches this message repeatedly:
How do you suppose it is possible to cause a "little one that believes in Christ" to stumble(be offended)? Could it be by making them aware of their sin?
Mark 9:42
42And whosoever shall offend one of
these little ones that believe in me, it is better for him that a millstone were hanged about his neck, and he were cast into the sea.
James 4:17
17Therefore to him that knoweth to do good, and doeth
it not, to him it is sin.
Having said all of that, there really isn't any Biblical or logical reason why an infant would be aware of their sin, let alone the vocabulary used to define sin. Where do you see, in contrast to awareness of sin, that babies have sin?