A Massachusetts woman who allegedly walked in on her husband while he was having sex with his mother on their couch says she always suspected an incestuous relationship was going on.

Tony allegedly told cops ‘it just happened’ and insisted it was the first time he had sex with his mom.

Tony’s wife, Lori Lavoie, told police that she ‘always had suspicions of the two of them having an intimate relationship.’

Lori told police that she had long wanted her mother-in-law to move out of the residence.

Cheryl reportedly said they had grown closer in recent months and started having sex when they began kissing.

The mother and son were living together in the same house at the time of the alleged encounter.

Police were called to reports of a disturbance at the property on May 20 and arrived on the scene to be met by the cousin of Tony’s wife.

The cousin told officers Tony’s wife had called her after she had walked in on her husband and his mom having sex in the property, police said.

When the officer asked the Lavoies why it had happened, Tony allegedly said: ‘I don’t know. It just happened.’

The 43-year-old then said he wanted treatment for it, according to police.

Lori told police ‘that she walked in on her husband Tony Lavoie having sex with his mother Cheryl Lavoie in the living room.’

After witnessing the alleged encounter, she told police: ‘I walked into my room and closed the door.’

The mother and son duo were charged with incest – a felony that carries a maximum sentence of 20 years in prison.

They made their first court appearance last Thursday where they both pleaded not guilty.