A woman who sexually abused her teenage stepson three decades ago has been jailed for the destructive impact her crimes had on him.

The woman, in her mid-20s at the time, initiated sexual activity three times over two years, before the boy's father discovered his wife and his son late one night in 1988 on the couch kissing, with their pants down and under a blanket.

What has been done cannot be undone. Credit:Cathryn Tremain

At that point, the father confronted his son. "Did you seduce my wife? Or did she seduce you?" he asked.

He then turfed his son out of the house and rang the boy's biological mother to collect him.