Chris Rock: Mystery Girl's Dad Says She Was NOT Adopted ... Mum on Money

The biological father of the 7-year-old girl who lived with Chris Rock and his estranged wife for 7 years tells TMZ the Rock family never adopted the little girl, but he refuses to say if any money changed hands.

Crispen Khanyile says his ex-girlfriend gave birth to Ntombi on February 23, 2008 ... this according to a private investigator's report commissioned by an interested party in the case. According to the report, both Crispen and the mother, Precious Ndebele, were unemployed at the time, living on the outskirts of Johannesburg.

The couple had 2 other kids and it appears the situation was increasingly desperate. When the private investigator interviewed Precious last year, she said she was living in a slum and selling secondhand clothes on the streets. The investigator said the conditions were "not conducive for human living."

Crispen would not discuss the arrangement with the adoptive parents, but simply said we should speak with Malaak, Chris' estranged wife.

It's interesting ... the P.I. says Crispen told him last year Ntombi was living with adoptive parents in the U.S., but when we spoke with Crispen on Wednesday, it was clear ... there was NO adoption.

As we reported, Ntombi has been living in the U.S. with the Rock family on a visitor visa, requiring her to return to South Africa once a year. Chris has not seen the girl since he split with Malaak and we're told he believes she did something shady to get Ntombi into the U.S.