Their daughter’s boyfriend Jonathan Jones was found guilty of their murders and sentenced to life in prison in 1995, but was later freed on appeal.
Jones, who was a self-employed recruitment consultant, had told police he had taken the day off work on the day the Toozes were killed and was in Orpington, Greater London.
His partial thumbprint was also on a cup and saucer that had been found in the couple’s living room.
He was arrested that December, five months after the murders.
The couple’s daughter stood by him, moving in with his family in Caerphilly after his arrest.
A year after his conviction, Jones was released on appeal. Three appeal court judges took five minutes to reach their decision.
The original trial judge was criticised, and it emerged police had failed to seal the crime scene properly.
South Wales police said the forensic review of the case, which is being led by the Major Crime Investigation Team, would continue.
Det Supt Mark O’Shea said the force remained “committed to solving these dreadful murders” and he encouraged anyone with information to come forward as it “may help us get justice for the family”.