A man severely affected by his violent stepfather's abuse as a child has been allowed to overturn the adoption order his stepfather signed 65 years ago.

A judge has also changed the man's name – to that of his birth father – after two half-sisters took DNA tests to confirm he was their brother and accepted him into their family.

The Family Court decision severing the man's links with the abusive alcoholic his mother married allows the man's birth records to be changed to show his true parentage, even though his mother, birth father and stepfather have all died.

"Your mother … must have been a strong woman and must have loved you very much," Judge Rachel Paul told the man, identified in her judgement as Gary Hess*.

"In a time when unmarried women did not keep their children and retain them out of wedlock, she kept you."

But Compton's mother, Debbie faced prejudice as an unmarried mother in the 1950s and Judge Paul said this may have led her to agree to marry 21-year-old Colin Hess, who was not her son's father.

In August 1957, Colin officially adopted the boy, who became Gary Hess.

But Judge Paul said that Colin subjected Gary Hess to physical threats and abuse, bullying, intimidation and sexual intimidation as he was growing up.

She said the stepfather showed no warm or caring emotional attachment to the young boy. He became "free labour" on the Hess farm and was exposed to frequent bouts of physical violence inflicted on his mother, partly driven by Colin's alcoholism.

Judge Paul said the abuse had "shadowed you throughout your life" and Gary Hess was "severely affected" by the treatment he was exposed to and suffered.

Gary Hess sought a discharge from the adoption order after accessing his adoption records in 2019.

The Ministry of Justice said obtaining a discharge from adoption can be costly and difficult and can be obtained only in limited circumstances.

However, Judge Paul cited case law which suggested an adoption could be cancelled if there was abuse by the adoptive father or a misrepresentation on the father's application that he was a "fit and proper person".

Finding these applied, the judge granted the discharge in the Family Court at Hamilton.

"Now that I have discharged that order I can give you a new name, and Mr Hess, this is the last time I will refer to you in that way," the judge said.

"From this point on, I refer to you as Mr Gary Compton. I am privileged to be the first person to call you Mr Compton."

The judge said the young Gary had once been taken to visit his birth father, Wilfred Compton. His two half-sisters by Compton had acknowledged him as their brother.

"More specifically – and I was, I have to say, impressed by this – your half-sisters must be very supportive of you in that they provided their DNA to be tested to see if you were their half-brother," Judge Paul said.

"That is a great show of generosity and of acceptance of you as part of the Compton family."

Judge Paul granted a paternity declaration so that Gary Hess' birth certificate could be changed to recognise Compton as his father.

"I know this has come late in your life, Mr Compton, but I hope that in some way the Family Court has lifted from you today some weight of your past," Judge Paul said.

"I wish you all the very best for your future."

*Names in this article have been changed by the Family Court to protect the subjects' identities.

- Ric Stevens, Open Justice