A former soldier has been found not guilty of murdering his ex-wife and her partner on Queensland's Gold Coast while their five-year-old child was in the home.

Christopher Robert Carter admitted to killing Renee Carter and Corey Croft in their Upper Coomera home in January 2015, but denied it was murder, arguing he had acted in self-defence.

The couple's bodies were discovered by a female relative, with their son alone in the home.

On Thursday, Supreme Court jury in Brisbane acquitted Mr Carter of all charges.

Outside court, he declined to speak to reporters.

Mr Carter's lawyer Peter Saggers said his client was grateful to the jury.

Police at the scene of the stabbing deaths in Upper Coomera in 2015. ( ABC News: Tom Forbes )

"One thing we did want to say is that Mr Carter's so thankful of the careful consideration that the jury gave the case," Mr Saggers said.

"Very emotional case. He is thankful that they gave it such careful thought."

The jury had heard there was friction between Mr Carter and his ex-wife because Mr Croft had a conviction for a serious offence involving a different child.

Earlier in the trial, the court heard a recording of a conversation between Mr Carter and police in which he admitted to stabbing the pair.

"I went there to f***ing talk to her and she came at me with a knife," Mr Carter said.

Defence lawyer David Brustman said his client did not deny he killed the pair.

"No issue whatsoever that this man killed the two deceased," he said.

"Killing per se is not murder."

Prosecutor Glen Cash told the court the five-year-old child did not witness the stabbing but "found that knife near his mother's body and moved it into the sink".

The jury took one day of deliberation to reach its verdict.

Mr Carter's supporters cried as the decision was handed down.