Scripture teaches that Children come from Hell. That means you, I and everyone else came from there.
The question is...
How did we end up there in the first place?
Let's begin with a few relative verses in order for us to being solving this Mystery...
Matthew 23:15
"Woe unto you, scribes and Pharisees, hypocrites! for ye compass sea and land to make one proselyte, and when he is made, ye make him twofold more the child of hell than yourselves"
In the above verse, we see Jesus Himself claiming that Children come from Hell... literally.
On top of that, Jesus seems to indicate that the Proselyte is going to have this happen to them more than one time by the use of the word 'twofold'.
In other words, they will be birthed twice into this world. Is there a limit to how many times this can occur?
What about good people? Seems being born from Hell only happens to Pharisee and hypocrite type folk.
Let's take a look at the first verse you quoted using the Amplified bible :)
15 “Woe to you, [self-righteous] scribes and Pharisees, hypocrites, because you travel over sea and land to make a single proselyte (convert to Judaism), and when he becomes a convert, you make him twice as much a son of hell as you are.
When Jesus spoke to the Pharisees in John 8:44-45 he said
44 You are of your father the devil, and it is your will to practice the desires [which are characteristic] of your father. He was a murderer from the beginning, and does not stand in the truth because there is no truth in him. When he lies, he speaks what is natural to him, for he is a liar and the father of lies and half-truths.