He was found as a new born baby by the church in Novigrad. There was a note only with a name on it, Sergey, but no last name was given. the priest who found him gave him a last name and it was Cerny, because he was wearing black baby clothes. He was send then to an orphanage in cernaya polana where he growed up.
It was a dark place, full of pain and despair, the children there were abused and raped by some workers and there came people sometimes, people with money and they paid to rape the kids too. He and a few others managed to escape but they had no luck and at the end Sergey was alone.
He survived in the woods for years, avoiding people and turning slowly into an animal, but this saved his life. Then the outbreak happends and everything changed but he is still alive.