A Bronx man subjected two teenagers to months of horrific abuse, repeatedly beating and threatening the youngsters while keeping them locked up in his apartment, prosecutors allege in a shocking new criminal complaint.

Michael Ramos, 34, was left to care for the siblings after his mother, who had adopted them, died in December — and he became their legal guardian, law enforcement sources said.

Police arrested Ramos Monday at his third-floor apartment on Burke Avenue following 911 calls from neighbors about a domestic dispute. Inside, they found the kids — a girl, 14, and her 13-year-old brother severely neglected and malnourished.

A defaced black Ruger 9 mm handgun was allegedly on the dining table, loaded with one round next to a 16-round magazine, the sources said.

Ramos allegedly taunted the siblings with the weapon, holding it to their heads and saying, “Someone is going to die today.”

“Do you want to die today?” he allegedly told them. “Open your mouth!”

If the youngsters refused, Ramos would allegedly pistol whip them in the apartment at the Eastchester Gardens public housing complex.

The children had not been allowed outside the East Bronx apartment since January, authorities said.

Ramos is also accused of using “a wooden bat, a metal bat, a black tension rod and an electrical cord” to beat the teens.

“On more than one occasion,” the complaint said, “the defendant would apply A&D ointment to his hands before putting on black motorcycle gloves and then repeatedly punched [the teens] about the head and body.”

Ramos also allegedly used a fork to jab the girl “on the right side of her face and knees,” causing “puncture wounds and small lacerations to the right side of her face and knees,” prosecutors said.

In addition, he is accused of using a Samurai sword to cut the girl in different parts of her body.

“These teenagers were treated horrifically,” one Bronx cop told The Post. “The suspect should never see the light of day again for what he did to these poor innocent kids.”

On Wednesday Ramos was ordered held without bail on Rikers Island at his Bronx court arraignment on charges of second-degree assault, unlawful imprisonment, endangering the welfare of a child, and several illegal gun charges.

Ramos had allegedly been taking sole care of the two teens since his mother died, according to the sources.

He has not yet been assigned a defense attorney, court records show.