Nicki Minaj Jelani Maraj

The 10-year-old brother of Jelani Maraj’s alleged rape victim testified that he walked in on the rape of his then 11-year-old sister and he knew what he saw “wasn’t right”.

The boy testified on day 3 of the rape trial of rapper Nicki Minaj’s brother in Nassau County Supreme Court on Monday.

Maraj, 38, is accused of raping his now 14-year-old stepdaughter as often as 4 times a week.

The youngster, wearing a black tuxedo and clutching a yellow star-shaped toy, testified that he walked in on the alleged rape of his sister in a basement bedroom in 2015.

“What happened was I was looking for [her]. “My pencil broke and I didn’t have any others,” the boy said. He described seeing his sister’s pants down “around her ankles,” and his stepfather’s underwear was “close to his knees.”

When asked by the prosecutor what happened next, the boy said he ran upstairs. He said Maraj later found him and slapped him in the face “about 10 times.”

The boy, who was 8 at the time, said he was told to keep his mouth shut about what he saw.

“He asked me if I had seen anything. I said, ‘Yes.’ He slapped me on the cheek,” the boy testified, as family members quietly wept in the courtroom.

Maraj then allegedly threatened the boy, telling him he would never see his mother again if he told what he saw.

At the time, Maraj was married to the children’s mother, Jacqueline Robinson.

“Jelani said I wouldn’t see her again if I told on him,” he said. “His face was kind of mad.”

The boy, whose bedroom was next to his sister’s, also described hearing his bedroom door suddenly close shut at night — and then his sister’s bed creaking.

Maraj’s lawyer, David Schwartz, tried to discredit the boy’s testimony by getting him to admit that the basement bedroom’s lights were off.

“You would agree that when the light is not on, the room is very dark?” Schwartz asked him.

“Yes,” the child answered.

The boy eventually told a school counselor about the abuse. The school alerted the police.

Prosecutors said Maraj’s DNA was found on a pair of the girl’s pajama pants.

On Friday a child abuse expert testified that the sixth-grader’s medical exam proves she was penetrated.

“I can say with a reasonable degree of certainty that (the girl’s) medical exam can prove penetration,” said Dr. Aaron Miller, who studied photos taken during an examination of the girl’s genital area.

Maraj was arrested in December 2015 and Nicki posted her brother’s $100,000 bond.

Nicky and her older brother are very close. She paid $30,000 for his wedding and she often shouted him out on her records.

Nicki plans to testify in her brother’s defense sometime this week.

Schwartz’s defense includes an alleged extortion plot by Maraj’s ex-wife, Robinson, whom he accuses of enticing Maraj to marry her so she could get her hands on Nicki’s money.

Schwartz claims Robinson tried to extort $25 million from Nicky to make her brother’s rape case go away.

“Why would [Robinson] lie and force her children to lie? I can give you 25 million reasons why,” Schwartz told jurors.

The trial continues on Tuesday.