Teenage couple murders girl's mother and sister, then watches 'Twilight'

A teenage couple convicted of murdering the girlfriend's mother and sister are believed to be the youngest double murderers in Britain's history.

According to the BBC, Kim Edwards and Lucas Markham, who were just named earlier this month after a judge lifted a ban on identifying them, were both 14 at the time of the murders, which took place in Lincolnshire, England.

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They were convicted of murdering Edward's mother, Elizabeth Edwards, 49, and her younger sister, Katie Edwards, 13, in April 2016.

Edwards helped her boyfriend construct the plan to murder her mother and sister and Markham carried out the murders, stabbing both victims a total of 10 times in the neck, BBC reported.

Edwards reportedly allowed her boyfriend to gain entrance into the home after he knocked on the window, a special signal to let her know when he arrived. She also coached him on how to quietly maneuver around the home to execute the murders.

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The pair reportedly had sex in the same house, reports say, took a bath and then watched the movie, "Twilight", after killing both females.

The two were arrested a day and a half later after reports emerged that the two had gone missing.

Now, audio from the police interrogations of Edwards and Markham, in which the teens apparently confessed to their crimes, is set to air in England, The Sun reported.

"I went into her mum's room and stabbed her in the neck while she was asleep on her side and smothered her face with a pillow," Markham reportedly said. "I went into Katie's room – which is the same room as Kim's – and I thought I stabbed her, but... I'm not a hundred per cent sure. It was, like, her on a mattress and then I smothered her face with a pillow too."

The report goes on to say that Markham admitted to killing Edwards' mother and later her younger sister so she wouldn't alert the police. When police asked him confirm if that was the sole reason, Lucas reportedly replied: "Pretty much."