A man has admitted to the murders of twin sisters and an elderly couple in North Yorkshire last summer.
Twins Diane (left) and Claire Sanderson were battered by Hobson
Mark Hobson, 35, killed his girlfriend Claire Sanderson and her sister Diane, and James and Joan Britton.
The twins were found in a flat in Camblesforth, near Selby, on 18 July - the Brittons were found later that day at their home in Strensall, near York.
Paul Worsley, prosecuting, said: "The circumstances surrounding these deaths are horrific and chilling."
The judge, Mr Justice Grigson, said he would sentence Hobson on 27 May. He faces life imprisonment.
Leeds Crown Court was told in a statement from the twins' parents, George and Jackie Sanderson: "They were our life, the reason we lived and worked. Now they are gone we have nothing."
Catherine Wilkins, a daughter of the Brittons, said her parents were elderly, but Hobson did not have the right to say when and how they would die.
Mark Hobson had a violent past
The court was shown handwritten notes made by Hobson which suggested he had planned the murders and was even planning to kill the twins' parents.
One note listed items used in the killings - another was a reminder for Hobson to ring Diane, who was lured to the house.
She was battered and subjected to a "macabre and bizarre" sexual attack, Mr Worsley said.
He said Hobson's friend Ian Harrison, who was Diane's boyfriend, came to his house and noticed the smell of the decomposing bodies.
Mr Harrison and the twins' father returned the next day and found the two bodies wrapped in bin bags.
In a statement read to the court, Mr Sanderson said he had wanted to cuddle Diane's body.
"I thought he had raped her. He had taken away her dignity from her," he said.
Home Office pathologist Professor Christopher Milroy found Claire had suffered 17 blows to the head with a blunt object such as a hammer.
Mr Worsley said Hobson had killed the Brittons in their own home in a totally unnecessary attack.
James and Joan Britton had both been stabbed in the back
After battering Mr Britton with his own walking stick and stabbing him, Hobson then battered and stabbed his wife.
Jeremy Richardson QC, defending, said: "This is a truly terrible case. The facts speak for themselves.
"The devastation caused to the family members is incalculable. I don't need to say any more in that regard."
Mr Richardson said the only issue to be decided was whether Hobson should spend the rest of his life in jail.
He said the only point he would be making with regard to this was that his client had pleaded guilty and had recently cooperated with the prosecution.