Acquire footage of a man. If it's on greenscreen, key it. If it's not, rotoscope it.
Duplicate your woman layer. Then rotoscope your footage of the woman in the car so the front seat, woman, and everything that should be in front of him is on one layer.
Place the man layer between the two woman/car layers.
Motion track the woman/car layer and apply that data to the man layer.
Or (better option) reshoot.
Before saying as other "reshoot", I just want to warn you: if you just have a picture of the guy (I assume your picture would be of the good guy sitting in a back seat of course), and want a realistic render, don't even bother to try the rotoscoping / keying / color correction: just reshoot. If you got a video footage of the guy in the backseat of the car or on green screen but sitting in the exact position with the exact lighting, then you can try the other solutions, but you should reshoot.