Ewen Macdonald was arrested after a nine-month manhunt that began when Mr Guy was shot dead at close range at the end of his driveway.
Macdonald always protested his innocence, indicating from his first court appearance that he would fight the charge.
The month-long trial ended on Tuesday but Macdonald remains in custody until he is sentenced for crimes he has admitted - some against Scott and Kylee Guy.
He has pleaded guilty to vandalising the couple's new home and burning another property of theirs to the ground.
In addition, he stole two deer from a neighbour and has pleaded guilty to three other charges.
The nature of those charges is suppressed until his next appearance in Palmerston North District Court on July 31.
Mr and Mrs Macdonald said the trial had been "brutal" for many people, especially Kylee Guy.
"Ewen knows he is responsible for that as well as the physical crimes he committed. Ewen has no words big enough to express his remorse or apologies."
When the verdict was delivered, Mrs Guy reacted by screaming: "He killed my husband, he killed my husband," then ran from the court.
The Macdonalds felt the media had forgotten "the real tragedy" of Mr Guy's death throughout the High Court trial and urged everyone to remember him - and those he had left behind.
"Wife, kids, mother, father, brother, sisters and wider families. Pause for a moment whilst you follow this spectacle and reflect on Scott's passing and all it means. We continue to give our unconditional love and support along with Bryan and Jo to Anna and our wonderful grandkids.
"We as a family have had enormous love and support from family, friends and colleagues which has given us the strength to get through the last months and these last four weeks. Thank you one and all."
Their family also received support from staff at Manawatu Prison, where their son was held since his arrest in April 2011. They said staff there had shown them respect, dignity and compassion.
"We have also had long hours with the New Zealand police giving statements and must say that they have been gracious and receptive to any of our concerns and have worked to resolve them all which has been greatly appreciated by us."
The Macdonalds' other son, Blair Macdonald, is a detective, a fact that was suppressed during the trial.