A 13-year-old Maryland boy has been charged with joining his 14-year-old girlfriend in trying to murder a relative — the first on a depraved kin “kill list,” according to a report.

The young pair were arrested in bloodstained clothing on the roof of a house in Manchester early Monday after a 56-year-old man had been battered with a hammer and stabbed in the neck, the Carroll County Sheriff’s Office said.

The victim — a relative of the boy’s — was taken to the University of Maryland Shock Trauma Center for treatment and will need reconstructive jaw surgery, according to the Carroll County Times.

The boy cannot be identified because he is a juvenile, and the charges against him have yet to be announced, the paper says.

Girlfriend Alaina Jade Blake — who turned 14 just this Saturday — is being tried as an adult, however, and the slew of charges against her include attempted first- and second-degree murder, court records show.

The unidentified victim was the first target on the pair’s “kill list” that was to target Blake’s grandparents and “possibly others,” prosecutors told a bail hearing Tuesday, the paper said.

The teens had a large amount of money and an overnight bag when they were arrested and planned to flee to Canada once their kills were completed, Carroll County District Court was told.

However, Blake also suggested that she planned to get her young boyfriend to kill her at the end of their planned carnage, according to the hearing, which Blake attended via video conference.

A motive was not given, the Carroll County Times said.

The teen girl recalled hitting the victim “multiple times” in the head with the hammer after sneaking into his bedroom with a night light, the paper said, citing charging documents.

The boyfriend told police that he heard a “blood curdling” scream, saw blood spurting out of his relative’s head — then stabbed him in the back of the neck with a curved knife, according to the report.

The victim was able to call 911 and cops found the teens on the roof, wearing bloodstained clothing and holding knives, according to the charging documents.

Blake has a preliminary hearing scheduled for Dec. 6. She is being held without bond and will be transferred to Thomas J.S. Waxter Children’s Center, a juvenile detention facility in Laurel, according to the report.

Her attorney, Judson Larrimore, declined to comment to the Carroll County Times.