Are we not all children of God? Yes, but we all won't be with Him for eternity. There is also a place called Hell.
The "key" to the door is held by the son of God, Jesus Christ. Who is he? Read the gospel of John, chapter one. If still doubtful, go to Hebrews chapter one. K.J.V.
This Jesus went to die on the cross for all people's sins. He must be received by you to enter into Heaven. See John 3:16 or Romans 10:9. Also throughout the Bible's New Testament. The war between good and evil will soon come to a close.
Did you ever wonder why the Jews are so hated? Most of the Bible was written by them. They are God's chosen people, Jesus was born a Jew and will return to Jerusalem to rule the world. Could it be because Satan is the prince of the world?
Read the book of Romans. Many of your questions will be answered there. Better still, read the Bible. It answers all questions. Read Acts 4:12.
Donald L. Caesar