The court heard how Liddle beat the youngest boy with his belt buckle, forced him into freezing cold baths and rubbed soiled pants into his face.
Liddle admitted wilfully mistreating the children between July 2002 and January 2004 at a home in Craigentinny.
Liddle changed his plea on the fourth day of a trial in which the court heard evidence of systematic abuse by the accused.
The children, who were six, seven and 14 at the time are now aged nine, 10 and 17.
After meeting Liddle the youngest began to suffer accidents and was severely punished for it.
Liddle repeatedly forced the boy to undress and bend over his bed or a chair. He then took off his belt and beat him with the buckle end leaving him with thick purple bruises.
On one occasion, the boy's 17-year-old sister, a nursing home care assistant, described seeing her brother fall to the ground screaming in agony.
"He kept saying 'I am sorry, I am sorry'" pleading with Liddle not to hurt him, but he paid no attention. Afterwards Liddle went into the living room and sat reading a magazine.
It felt as if we were living in a prison camp
A victim of Liddle
She said Liddle shouted and swore at her for minor matters like calling a sink a bunker and for the way she wrapped a flex around an iron.
"I felt like I couldn't do anything in the house, everything I did was wrong. It felt as if we were living in a prison camp.
The children's mother said Liddle was a "control freak" who would not even allow the children to chat during meals and who spent his time reading magazines and drinking whisky.
She said she had contemplated committing suicide because of his actions.
Defence agent, Grant Markie, told Sheriff Isabella McColl that Liddle had been suffering emotional and mental health difficulties at the time, but he accepted that his behaviour had been a significant breach of trust.
Sheriff McColl said because of the lateness of the guilty plea, the children had had to go through the ordeal of giving evidence.
The behaviour of the little boy, she said, had become so disturbed that he was sent by his school to psychiatric services at the Royal Hospital for Sick Children.
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