The family of an 84-year-old woman murdered by her daughter and grandson have spoken of their "shock and horror" at finding out the circumstances of her death.
Former soldier Barry Rogers used a pillow to smother Betty Guy after his mother Penelope John had given her a cocktail of pills and whisky on November 7 2011.
Mrs Guy's death was initially thought to be from natural causes and no post-mortem examination was carried out.
Rogers, 33, and John, 50, came under suspicion four years later when an ex-partner of Rogers told police he said he had killed his grandmother by putting a pillow over her face.
The pair denied murder but were convicted by a jury of five women and seven men following a trial at Swansea Crown Court.
Speaking after the verdicts on Tuesday, another of Mrs Guy's children, Lorraine Matthews, said justice had prevailed.
"Seven years after my mother's death, my brothers, my sons, myself and other members of the family, were shocked and horrified to learn from the police that my mother, Mrs Betty Guy, may not have died from natural causes and that my sister and her son were to be charged with her murder," she said in a statement released by Dyfed-Powys Police.
"Over the past three years the police have worked tirelessly to collect sufficient evidence to bring this case to court.
"Now that the case has drawn to a close we are satisfied that justice has prevailed and now we can close this very sad chapter in our lives."
The investigation was launched after Rogers' former girlfriend Sandra Adams reported him to the police.
Officers found two other previous partners of Rogers who said he had told them about his part in Mrs Guy's death.
John, of St Dogmaels, Pembrokeshire, and Rogers of Fishguard, Pembrokeshire, were arrested on October 6 2016 and while they were in custody officers installed covert recording equipment in John's home while they were in custody being interviewed.
In his opening, Paul Lewis for the prosecution, told the jury they would hear the pair "discussing Mrs Guy's death in terms which were inconsistent with her having died naturally and peacefully".
At one point Rogers could be heard saying to his mother: "You have got nothing to worry about, it's me that's the one that's done the act."
Speaking after the verdict Gemma Vincent, from the CPS, said: "Covert recordings such as these are not common.
"In this case it provided compelling evidence for the CPS to present to the jury, demonstrating that the killing of Betty Guy was deliberate and planned.
"Ms Guy's life was cut short by her own daughter and grandson - our thoughts and sympathies are with those affected."
The judge in the case, Mr Justice Lewis said both Rogers and John would receive life sentences of imprisonment.
He said he would look at the authorities on mercy killings in preparations, despite both defendants having denied killing Mrs Guy for any reason, including a mercy killing.
He said: "You have been found guilty of the murder of Betty Guy.
"I order that both of you be remanded in custody.
"I direct that you be brought back to court on Thursday February 8 whereupon I will sentence you to the sentence required by the law which is life imprisonment and the appropriate minimum term."
Rogers and John were remanded in custody to appear before the court for sentence on 10.30am on Thursday.