The court heard they sold the boy - who is now 10-years-old - on the darknet, a part of the internet that can only be accessed using special software.
In Tuesday's verdict, the couple were ordered to pay a total of 42,500 euros (£38,000) in compensation to the boy and another victim, a young girl.
The disturbing case sent shockwaves through the country as authorities were accused of failing to protect the boy.
The 48-year-old mother will not appeal her 12-and-a-half-year prison sentence because she wanted to signal to her 10-year-old son that "things would be quiet now", her lawyer Matthias Wagner said.
German prosecutors have also gone after other suspected members of the pedophile ring.
Her husband Christian Lais, the boy's stepfather whom he called "papa", received a 12-year sentence followed by preventive detention.
The mother's partner, who already had a previous conviction of serious child abuse, confessed to the court in June that he was the "driving force" behind the crimes.
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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.
A German court Tuesday handed down lengthy jail sentences to a couple for repeatedly sexually abusing their young son and selling him to paedophiles online for more than two years.
The stepfather has a previous conviction for paedophilia.
The couple were found guilty of rape, aggravated sexual assault of children, forced prostitution and distribution of child pornography between May 2015 and August 2017.
The mother was often near the scene of the abuse by other men "to exert a calming influence on her child", and in the case of one client participated herself, the court said.
The judge, Stefan Bürgelin, said the child's mother started abusing her child after her partner, Christian L, threatened to leave her.