Nathan Carman was hailed as a hero after surviving 5 days at sea. But was it all a lie?

After a week of floating in a life raft at sea, Nathan Carman spotted a freight ship.

The ship’s crew rescued him and he boarded the vessel, soaking wet and 160 kilometres from where his boat Chicken Pox sank.

He ate his first hot meal in days and as crew members gathered to hear his story, he expressed concern about his mother.

Nathan and Linda Carman had set off the coast of Long Island, heading for Martha’s Vineyard, a small island in the Atlantic Ocean not far from Cape Cod, but their boat started taking on water and quickly sank.

Nathan told authorities he made it onto a life raft but when he turned around, he couldn't see his mother.

From the freighter, Nathan asked the US Coast Guard if they had found her. They hadn't, and nearly three years on from that conversation, Linda's body has still not been found. She is presumed dead.

In the years that have followed, Nathan's story has gone from one of survival to a much darker, more complicated tale.

Linda's three sisters, as well as the company that insured Nathan’s boat Chicken Pox, have cast doubts over his story, alleging he purposely tampered with the boat, causing it to sink with his mother onboard.

And that's not all: His aunts alleged Nathan killed not only her, but his millionaire grandfather John Chakalos too.

Nathan's aunts - Valerie Santilli, Elaine Chakalos and Charlene Gallagher - have filed what is known as the "slayer petition" alleging Nathan killed his grandfather, John Chakalos, in 2013 and was responsible for the death of his mother, Linda, in September 2016.

Three years before Linda disappeared, her son was a police suspect in his grandfather's 2013 murder. Chakalos was shot by a gun that fires the same caliber ammunition as the bullets of a rifle purchased by Nathan shortly before the shooting.

Nathan has not produced the weapon and lawyers for the insurance company alleged he disposed of it on the fishing trip where his mother disappeared as part of his plan to inherit millions of dollars. He has also refused to take lie detector tests, which his aunt's lawyer Dan Small called "shameful".

"Nathan’s shameful attack on his grandfather shows there is no depth to which he will not sink to avoid producing his gun, which is the probable murder weapon," Small said.

"Now he is trying to cast blame on his own aunt, even though she willingly took and passed a police lie detector test, while Nathan refused, and she cooperated fully and honestly with the police, while Nathan lied repeatedly, including about this very gun.

"Every day that passes in these legal proceedings shows even more clearly that Nathan’s behaviour is calculated, evasive, and ultimately, guilty."

Nathan was named as a suspect in his grandfather's murder case but a warrant for his arrest went unsigned.

With their petition, his three aunts want a judge to deny him access to what would amount to more than $7 million in inheritance, but Probate Judge David D. King ruled that since Linda's body has not been found and she's not legally dead, he may not be able to act on it.

Nathan denies anything to do with the crimes.

His lawyer David Anderson pointed to CCTV footage which shows Nathan at a local convenience store and then at home around the time his grandfather's neighbour heard a loud bang coming from Chakalos' residence.

"Simply stated, if John Chakalos was shot at 2am, then Nathan Carman clearly was not the murderer," lawyer David Anderson said, the Hartford Courant reported.

Meanwhile, Nathan has also been sued by his insurance company.

Court documents filed by National Liability and Fire Insurance Company in December 2017, accused Nathan of tampering with Chicken Pox before he and his mother set out on their doomed fishing trip. The company is refusing to pay out the $85,000 the boat was insured for.

The documents claim Nathan enlarged four holes in the hull "near the waterline and attempted on his own to fill them, which was not satisfactory," the Boston Herald reported.

The insurance company's lawyer David Farrell Jr said that like the holes in the boat, Nathan's problems have also grown.

"No wonder the boat sank and Carman’s mother died."

In June, a judge will examine the case against Nathan all over again, despite the fact he has never been charged over either his grandfather or mother's deaths.