OK SO I LIED I WILL MAKE MANY MUCH FEELS MWAHAHA FEEL MY WRATH
From between the ages of twelve to twenty three were a blur to Dean, filled with much death and suffering.
Dad on a hunt and about to die? Take the hit.
Someone picking on Sammy? Not like he can truly loose.
Not enough food? He can go through a few months without eating, that's fine. Unpleasant but it's better than anything happening to Sam.
It's not like it was a big deal though.
The issue arose when Sam left. John was upset.
John may have taken it out on him, and there was no way he didn't notice his lack of pulse.
From that point on they split up, occasionally talking (out of guilt for killing his son Dean assumed) not seeing each other again in about four years.