On What Basis Do You Think You’re a Child of God If Not That You’re Born Again by Spirit of Elohim Through Son Jesus?

Many say that we are all children of God, but Jesus said many will go to hell, so why would He send His children to hell when He’s said that His children will be with Him in heaven? Why would Jesus Christ have allowed Himself to be killed on the cross (then resurrect) if there are many ways to avoid hell?