Mrs Clay, 73, and Mr Hill, 74, were camping together when they disappeared from Bucks Camp in Victoria's Wonnangatta Valley in March 2020.
Greg Lynn is accused of killing the couple, whose remains were later found in bushland near the Union Spur Track, near Dargo.
The 57-year-old man, who was a Jetstar captain at the time, has pleaded not guilty to two counts of murder and is on trial at the Supreme Court in Melbourne.
Carol Clay and Russell Hill were camping together when they disappeared in the Wonnangatta Valley. (HANDOUT/VICTORIA POLICE)
Mr Hill and Mrs Clay were in a relationship for 14 years at the time of their deaths, the woman's daughter Emma Davies told the jury on Wednesday.
"They'd known each other from childhood, Russell was mum's first boyfriend," she said.
"She said it was a very caring and very loving relationship."
Police contacted Ms Davies on March 29, 2020, about nine days after the alleged murders, to ask if she knew whether her mother was.
"I said I didn't know," she told the jury.
The police officer asked for Ms Davies' consent to send out a missing person's report to the media about her mother's disappearance, the jury was told.
Ms Davies said she had privacy concerns about that because Mr Hill was married to another woman.
"Russell was married and so I was concerned about the media release going out and showing them camping together," she said.
Dermot Dann said the two deaths were accidental and Lynn made "terrible choices" afterwards. (James Ross/AAP PHOTOS)
Mr Hill's friend of 30 years, Michael Allan, said he spoke to him over high frequency radio about 6pm on March 20, hours before it's alleged he and Mrs Clay were murdered.
"We just generally spoke about how lovely it was being in the Wonnangatta Valley and about the day's activities," Mr Allan told the jury.
Mr Hill's demeanour was "quite normal, nothing seemed untoward", he said.
Prosecutors have claimed Lynn intentionally killed the couple and told the jury this would be proven beyond reasonable doubt due to his conduct after the alleged double murder.
But his barrister said the deaths were accidental and Lynn made "a series of terrible choices" after their deaths, including burning their bodies and campsite.
Dermot Dann KC on Tuesday said Lynn and Mr Hill got into an argument and the 74-year-old had threatened to show police footage of Lynn deer hunting close to the camp.
He alleged Mr Hill took a gun from Lynn's car and accidentally shot Mrs Clay in the head and then came at Lynn with a knife.
Lynn claimed he was trying to defend himself from the knife when it went into Mr Hill's chest, Mr Dann said.
"I haven't behaved well, I've made some poor decisions, but murder, as I understand it, I'm innocent of," Mr Dann said Lynn told police.
The prosecutor pointed to the conduct of Lynn after the deaths as evidence of murder. (James Ross/AAP PHOTOS)
However, prosecutor Daniel Porceddu put forward an alternative version of events.
He said Mr Hill was killed first and Mrs Clay's death happened after she had "witnessed or been aware of Mr Hill's violent death".
He pointed to Lynn's conduct after the deaths as evidence he committed murder, including not calling for help, contaminating the scene and concealing evidence.
Earlier on Wednesday, several campers who had met Mr Hill and Mrs Clay in the weeks before their deaths gave evidence.
Chris Benton, who met Mr Hill while he was camping alone at King Billy campsite on March 11, described a conversation with the 74-year-old about life after retirement.
"He did go on to say that retirement did 'f*** him up', he actually put his head down when he said that remark," he told the jury.
The trial continues on Thursday, with two weed sprayers and two more campers to take the witness stand.
