From what I understand, God is in control of who is born and the details of their creation such as when, where, how, etc.
This is just tradition and mythology with no connection to scriptural truth. You are making a common, and extremely damaging mistake that runs rife through both church and society.
God handed dominion of earth over to mankind through Adam. Adam surrendered that sovereignty to Satan, which is why, referring to Satan, Jesus said.-
Jn14v30
No longer will I speak much with you; for the ruler of this world comes, and in Me he has nothing.
Given that Jesus told us that Satan was the ruler of the world, maybe we should start blaming Satan for all the world's ills instead of God! Or blame mankind for submitting to Satan's ideas.
So, as far as God controlling births etc., -
If someone's birth is the result of rape, then the rapist was in control, not God.
If someone's birth is the result of promiscuity, then both partners were in control, not God.
God obviously has foreknowledge of everything that will happen at any time, but that doesn't mean that God makes it happen. God is not a rapist, or a control freak.
He also has perfect for knowledge, I believe, since he is omniscient, and not time bound like we are. So He knows how each person will respond to each situation he/she faces.
Agreed, but God's foreknowledge is totally different to God controlling the response man will make to each situation.
He knows if a specific circumstance will draw a person to believe in Jesus, or if a specific circumstance will create a negative or evil response from someone.
So, my question is: how can unbelievers be held responsible for their sin when He made them...
No no no... We were made by our parents. That's why we look like our parents and have their mannerisms etc.
Our will is always free, within of course the constraints of our fellow man.
and placed them in those circumstances even though He knew that they would harden their hearts against Him and end up going to hell?
Certainly God can and does bring circumstances about where we need to make choices, and equally, God knows what those choices will be, and makes use of them to further His own purposes.
But God will never put his hand inside a man's heart and flip the "obedience/rebel switch" either way. Man alone has power over that internal switch.
We have a God given a conscience through which the Holy Spirit convicts every man woman and child on the planet. The more we go against that conscience, the more our spiritual deafness and blindness grows. We are responsible for those choices, not God. And God holds us responsible with no excuses.
Romans1v18For the wrath of God is revealed from heaven upon all ungodliness and unrighteousness of men, suppressing the truth in unrighteousness, 19because the known of God is manifest among them, for God has revealed it to them. 20For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse.