Nicki Minaj’s brother’s former stepdaughter testified in chilling detail Monday how he repeatedly raped her in their Long Island home beginning when she was just 11 years old.

She also unloaded the grief she’d carried since her younger brother walked in on one of the attacks.

Jelani Maraj, 38 — who allegedly threatened to have the girl taken away from her mother if she did not comply with his sick plans — even instructed her on how to make anal sex less painful as he raped her, the victim, now 13, said in court.

“He would call me his puppet and [say] I had no say in what he did to me,” the girl said, wearing glasses and with her hair pulled back in a ponytail on the stand.

The abuse began in April 2015, when she was living with her mother and stepdad Maraj on Long Island, the girl said. He started by rubbing his erection on her, but things escalated when the young girl innocently went to his room to greet him one morning that month, she said.

“It was a Saturday morning,” she said. “I had went to him to go say ‘Good morning.’ I had hugged him as usual. I went to go lie next to him as I usually do. When I did that, he told me to go close the door. He told me to take off my pants. Then he told me to come under the covers with him and he started caressing me.”

Maraj then had sex with the preteen and ejaculated in her mouth, she said. He then allegedly began frequently raping the little girl after school.

“We would have sex in his bedroom, in my bedroom, in the basement,” she said.

Maraj tried to make her think the attacks were her fault, telling the young victim she was sending him signals, she told the court.

“He had mentioned I was brushing myself on him and that I wanted it to happen,” she said.

Maraj started sodomizing her over the summer, she said.

“He used lubricant and told me to breathe properly and not to clench so it wouldn’t hurt so much,” she said. “It hurt. I told him to stop and tried to push him away.”

She also detailed that she “was on my forearms on the bed and my pants were pulled down” at the moment her then-8-year-old brother caught Maraj in the act — and how she had to tell the youngster not to talk for fear they’d be “sent away.”

Maraj’s lawyer David Schwartz has claimed that the girl’s mother, Jacqueline Robinson, instructed her children to lie to extort $25 million from Minaj.