The brother of the tragic Long Island boy left to freeze to death in an unheated garage has detailed the heartbreaking abuse he claims was handed out by their NYPD cop dad charged with the boy’s murder.

In two YouTube videos released by his mom, Andrew Valva, 6, recalls the tortured life he and his two older brothers were put through while living with dad Michael Valva and his fiancée, Angela Pollina — abuse being blamed for the death of the ex-cop’s 8-year-old autistic son, Thomas.

Andrew calmly tells his mother, Justyna Zubko-Valva, how his brothers were made to sleep in a garage as cold as “snow” with no pillows and rarely getting fed — and had bruises “everywhere” from regular beatings.

They were thrown in the garage for “peeing on themselves” — with the boy saying that only happened because they were not allowed to go to the bathroom for days on end.

But they were terrified to report their abuse, he says in the videos, because “then they would be punished for three days.”

“Staying in the room for three days, not going pee, and not doing anything. And getting slapped in the butt,” he calmly told his mom, saying that “Dad beat them up” and even left head wounds.

Andrew said his brothers — Thomas as well as Anthony, 10 — were made to stay in the garage in the Center Moriches home “every day.”

“All day and every day,” he said, replying when asked how often they were allowed out: “Never.”

He said there was not a heater, calling the garage “just plain old cold” and “like snow in there” — and with no comforts for the kids to sleep on.

“Just the floor. And no pillow. And no blanket, either,” he told his mom.

They were also fed “only once a day,” Andrew told his mom. “Just a sandwich. That’s it,” he said.

His mom got most upset when Andrew explained that his brothers were left in the garage because they “kept peeing on themselves” — then explaining that it only happened because “they wanted to go pee and Mom and Dad wouldn’t allow them.”

“And they kept on peeing in their pants because they weren’t allowed to go in the middle of the night to the bathroom,” he told his mom, who sobbed, “Oh my God!”

Zubko-Valva said in her caption that she released the videos as proof that Thomas’ death in January “was NOT an accident but the tragic result of many years long non-stop sadistic abuse.”

Valva’s court-appointed lawyer has claimed the death was “a nightmarish accidental death and clearly not a murder.”

But Zubko-Valva wrote, “The garage was freezing and unheated, my children were locked in the garage without possibility to get out or use the bathroom, and they were forced to sleep on concrete floor without mattress, blankets, or pillows. The justice for Tommy, Anthony, and Andrew needs to be served!”

The two-part video ended with Zubko-Valva reassuring her son he was “safe now” and thanking him for talking.

“You’re welcome,” he says.