According to Metro UK reports, Monica Mares, 37, and Caleb Peterson, 20, were found to be committing incest after a neighbour in Clovis, New Mexico, reported them to police.
They were due to face trial but pleaded guilty at the final hour after accepting a plea deal for three years probation with 18 months supervised.
They were also told to stay apart for 18 months and Mares was also told to stay away from her nine other children.
The mother and son couple decided to go public with their affair last year in order to raise awareness of Genetic Sexual Attraction (GSA) and make it legal for them to have a s*xual relationship.
Mares gave birth to Caleb, who was born Carlos, when she was 16 years old and gave him up for adoption soon afterwards.
She met him for the first time since at Christmas 2015, after the pair got in touch over Facebook.
Caleb moved in with her and says he fell in love with her in part because she looked after him.
‘I never had anyone cook me meals or give me anything,’ he told the Daily Mail. ‘I never got anything my entire life and she went out of her way to make me happy.
‘After about a week or so I started having feelings for her, and I guess I fell in love.’
The mother-of-nine reciprocated, and now says she would readily give up the right to see her other children if she was asked to choose between them and Caleb.
‘The first time we were physical we ended up holding hands, and then we ended up kissing – and the kissing led to other things,’ she said.
‘I felt comfortable with him and we fell even more deeply in love.’
But Mares says she’s afraid to go out because people in her town know about the relationship, and threaten her and call her names.
Caleb’s personal life has suffered too. Since the affair became public, his dad walked out on him.
The two were interviewed separately so as not to breach their court ordered separation.
The teenager said: ‘If I could speak to her now, I would say to her: “I love you and I miss you and I can’t wait to see you again”.’