Ok, Adam is not the direct son of God, it's like saying a lion is a child of God just because God made the lion. That applies back to Adam, however, Jesus is the Son of God, only because hod but Jesus into a mortal womb and giving Jesus a Mortal Body. If you are also wondering why Christians call ourselves Children of God, it is because if we accept Jesus. His blood covers us, so God will only see the blood of Jesus, his son, so God will see us under the protection of Jesus, and as his own children Hope this helps!Why God creating Adam w/o any parents does not make God his father/mother but God creating Jesus w/o father makes God his father?
Maybe Jesus was a great but fully human prophet (just like Adam, Noah, Abraham, Moses, ...)?
All religions are a belief and magic!