Ms 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 murdering the couple, whose remains were later found in bushland near the Union Spur Track, near Dargo.
The 57-year-old man, who was a captain with Jetstar at the time, has pleaded not guilty to two murders and is on trial in the High Court in Melbourne.
Mr Hill and Ms Clay had been dating for 14 years at the time of their deaths, the woman's daughter, Emma Davies, told the jury on Wednesday.
“They had known each other since they were kids, Russell was mom's first boyfriend,” she said.
“She said it was a very caring and loving relationship.”
Police contacted Ms Davies on March 29, 2020, around nine days after the alleged murders, to ask if she knew if that was her mother.
“I said I didn't know,” she told the jury.
The police officer sought Ms Davies' permission to send a missing person's report to the media about her mother's disappearance, the jury was told.
Ms Davies said she had privacy concerns because Mr Hill was married to another woman.
“Russell was married and so I was concerned about the media going out and showing them camping together,” she said.
Hill's 30-year-old friend, Michael Allan, said he spoke to him over high-frequency radio about 6pm on March 20, hours before he and Ms Clay were said to have been murdered.
“We talked generally about how beautiful it was in the Wonnangatta Valley and about the day's activities,” Mr Allan told the jury.
Mr Hill's behavior was “very normal, nothing seemed untoward”, he said.
Prosecutors have alleged that Lynn deliberately killed the couple and told the jury that would be proven beyond a reasonable doubt because of his behavior after the alleged double murder.
But his lawyer said the deaths were accidental and that Lynn made “a series of terrible choices” after their deaths, including burning their bodies and their campsite.
Dermot Dann KC said on Tuesday that Lynn and Mr Hill got into an argument and that the 74-year-old had threatened to show police footage of Lynn deer hunting close to the camp.
He claimed that Mr. Hill took a gun from Lynn's car and accidentally shot Ms. Clay in the head, then came at Lynn with a knife.
Lynn claimed he was trying to defend himself from the knife when it plunged into Mr Hill's chest, Mr Dann said.
“I have not behaved well, I have made some bad decisions, but of murder, as I understand it, I am innocent,” Dann told police.
However, prosecutor Daniel Porceddu offered an alternative version of events.
He said Mr Hill was killed first and Ms Clay's death occurred after she “witnessed or was aware of Mr Hill's violent death”.
He pointed to Lynn's behavior after the death as evidence that he committed murder, including failing to call for help, contaminating the scene and concealing evidence.
Earlier on Wednesday, several campers who had met Mr Hill and Ms Clay in the weeks before their deaths gave evidence.
Chris Benton, who met Mr Hill while camping alone at the King Billy campsite on March 11, described a conversation with the 74-year-old about life after retirement.
“He went on to say that his retirement confused him, he put his head down when he said that comment,” he told the jury.
The trial continues on Thursday, with two weed sprayers and two more campers taking the witness stand.