On tumblr I wrote for each one:
Revenge, curiosity killed the cat, traumatic event, escaping captivity, one stolen eye, bullied, dishonor, addiction, isolated and regret.
I didn't want to write too much so I try to sum their back story with a few words. I have a pretty good idea what had happen to all of them when they were kids.
Can you guys guess what happen to each one based on the terms I gave for each one? :]
In order just in case: Spy, Engie, Pyro, Heavy, Demo, Sniper, Soldier, Medic, Pauling, Scout.