The estranged wife of Nicki Minaj's brother has been accused of framing her husband for raping her daughter as part of a $25 million extortion plot.

Jelani Maraj was arrested in December, 2015 amid allegations he had sexually assaulted a 12-year-old girl for months.

Specific details surrounding the case were kept under wraps until his trial began in Nassau County Court, New York on Thursday (19Oct17), when it was revealed the child at the center of the claims is his stepdaughter.

Maraj, who has pleaded not guilty to the charges, had married the girl's mother, Jacqueline Robinson, in August, 2015, in a lavish wedding paid for by hip-hop superstar Nicki.

In the trial's opening statements, prosecutors told the court the girl's younger brother, then eight, had exposed the abuse to child services officials, claiming he had been beaten after walking in on Maraj having sex with his then-11-year-old sister in a spare bedroom at their family home.

The accusations were reported to police, who executed a search warrant on the house and found a pair of the girl's pyjama bottoms with evidence of Maraj's DNA.

"He had sex with that 11-year-old girl sometimes four times a week," Assistant District Attorney Emma Slain told jurors.

However, defense attorney David Schwartz insists Maraj was targetted by Robinson, and was set up so she could allegedly blackmail the No Frauds hitmaker.

He told the jury Robinson planted the DNA and made sure officers found the clothing during their search of the property.

"Why would (Robinson) lie and force her children to lie? I can give you 25 million reasons why," Schwartz said, alleging Robinson had "related to Nicki that, 'I can make the charges go away for $25 million.'"

"Jackie became obsessed with Nicki Minaj - getting her hands on her money," he continued. "An evil Jackie targeted (Maraj) trying to get him to marry her, and then just four months after they were married, we have this."

Nicki has not commented publicly on her brother's legal trouble, but she previously showed her support by putting up two of her homes for collateral to cover his $100,000 bail.

According to the New York Post, Nicki will be taking the witness stand to back up the extortion story, although her court appearance has not been confirmed.

The trial is expected to last for up to three weeks. If Maraj, 38, is convicted of felony second-degree course of sexual conduct, he could be placed behind bars for life. He is also fighting a misdemeanor count of acting in a manner likely to injure a child.

Robinson filed for divorce in August, 2016, just four days before the couple's first wedding anniversary.