The couple, who identified only as Berrin T and Christian L, lived in the town of Staufen near Freiburg, Germany, and were paid up to €10,000 (£8,950) a time to abuse their son.
The mother of the boy, Berrin T., 48, and her partner Christian L., 39, will serve twelve-and-a-half-year and twelve-year prison sentences respectively for selling Berrin's son on the area of the internet that can not be accessed by search engines.
Her partner, Christian L., was sentenced to 12 years. Some of the abuse was filmed.
The case came to light following an anonymous tip-off last September, and led to the arrest of eight people who have been charged with belonging to an online paedophile ring.
The stepfather has a previous conviction for paedophilia, the AFP reported.
The court found that the unemployed couple had sexually assaulted the boy, now 10, and pimped him on the so-called dark net between May 2015 and August 2017.
On Monday, the same court sentenced a Spanish paedophile, Javier Gonzalez Diaz, to 10 years' prison for repeatedly sexually abusing the young boy after paying the parents. The girl, who had mental health issues, had on several occasions been given to the 48-year-old woman by her mother to care for her.
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He also made serious accusations against the child's mother.
The couple distributed videos of the sexual abuse across the dark net, selling it for large sums of money.
The verdict against the mother and stepfather in the case, which police have called one of the most atrocious they have investigated, is expected on Tuesday.
Local authorities have been accused of failing to protect the boy, who now lives with a foster family.
The Freiburg court also ordered the two abusers to pay 42 500 euros (49 200 dollars) in damages to the boy and a young girl, another victim in the case.
The woman's partner was supposed to be banned from having contact with children, due to his previous conviction.