Maraj has been accused of raping his stepdaughter, who is now 14, as many as four times a week for years before he was arrested in 2015.
But defense claims that Maraj, who is Nicki Minaj's older brother, is a pawn in a $25million extortion plot against the rapper by his accuser's mother, Jacqueline Robinson.
The 10-year-old told jurors on Monday that in 2015 he walked into a basement bedroom of his home, looking for his sister, who was 11 at the time.
'My pencil broke and I didn't have any others,' the boy explained about why he went looking for her.
He said he found his sister's pants 'around her ankles' and Maraj's 'underwear close to his knees.'
'I thought it wasn't right,' the boy said about what he saw. 'It looked weird to me so I ran upstairs.'
The boy then claims Maraj later came to find him and slapped him in the face 'about 10 times.'
He said Maraj asked him if he'd seen anything, and slapped him on the cheek when he replied 'yes'.
Maraj allegedly then threatened the boy would never see his mother again if he wasn't silent.
'Jelani said I wouldn't see her again if I told on him,' he said. 'His face was kind of mad.'
The little boy also told the court that sometimes at night he would hear his bedroom door close, and then his sister's bed creaking. He said their rooms were next door to each other.
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