Japheth Dury is who John Beecham really is he came from his parents Victor Dury and Mrs.Dury who doesn't have a name that was mentioned. He had an elder brothe named Adam Dury who he is no longer in contact with and they both know nothing of each other in their adult lives.
It is said that Mrs.Dury was always cold to her child Adam theorized because she didn't really want kids, she didn't abuse him but was cold and distant only doing what was expected of her. Japheth was a different case he was concieved in his fathers drunkened rage where he assualted Mrs. Dury causing a rift in his relationship with both parents before he was even born. When he was eventually born he was hated by both parents because he was a symbol in a way of Victor Dury's lust and his actions. From what Adam said he was uncared for and heavily beaten for any actions he commited, it seems he was targeted by his mother due to her hatred for him.
Adam stated that he tried to get the boy out of the house whenever he could by taking him moutaining where he found a rather disturbinng thing about his mental state. Japheth enjoyed trapping small animals and then torturing them, Adam said it was the only time he didn't have that tic in his face when he was in the moutain or killing and animal. Adam said he tried to sway him away from these behaviors but he never believed he did.
Becoming a bad man
Adam says a time where he and Japheth had found a man named George Beecham who had gained both of there trust especially Japheth's. He says that one day he trusted the man to stay with Japheth while they were in the moutain while he went out to do something. But upon returning he found George Beecham gone and Japheth half naked and baring signs of assualt.
His first murders

In my opinion while Japheth was a horrible man in his adult years there were many events that shaped his violent mind things that could've been prevented. But my sympathy only goes out to the young boy who was ruined by the cruelties of the world and a society that failed him. I feel no sympathy for the sadistic monster he became.