Police have released a photograph which they believe may show canoeist John Darwin during the five years that he was missing, presumed dead.
Mr Darwin has appeared in court, accused of making an untrue statement to get a passport and obtaining £25,000 in life insurance by deception.
Mr Darwin's wife Anne, 55, was arrested on suspicion of fraud on Sunday.
Police said there was nothing to suggest that the couple's two sons were anything other than "victims".
Det Supt Tony Hutchinson of Cleveland Police said the photo showed Mr Darwin with a "large bushy beard".
During a press conference, Mr Hutchinson added Mr Darwin may have used the name John Jones, and urged any members of the public who remembered him to come forward.
He expressed sorrow for Mr and Mrs Darwin's sons, Anthony and Mark, who he described as "victims".
"If that is the case, they have been duped in what can only be described as a really disgraceful fashion," he added.
"They have believed for the last five years their father was dead.
"So I feel dreadfully, dreadfully sorry for them."
Mrs Darwin has been questioned by officers at Hartlepool police station after returning from Panama.
Mr Hutchinson said that on the journey to Cleveland she "was pale, drawn and very quiet - which is understandable".
Earlier, Mr Darwin was remanded in custody at Hartlepool Magistrates' Court.
He spoke only to reply "correct" when asked to confirm his name.
Mr Darwin will make another appearance in court via a videolink on Friday. He was arrested at his son's house in Basingstoke, Hampshire, on Tuesday.
The canoeist was declared dead by the Hartlepool coroner in 2003.
Anne Darwin is being interviewed by police after returning to the UK
Mr Darwin appeared in the dock accompanied by a single security guard during the brief magistrates' court hearing.
The first charge he faces is that on 16 May 2003 he fraudulently obtained £25,000 from Unat Direct Insurance Management Limited by deception, by falsely representing that he had been killed in an accident on or about 21 March 2002.
The second charge he faces relates to making statements known to be untrue to obtain a passport.
Mr Darwin did not enter a plea and there was no application for bail made.
The chairman of the bench, Alan Langshaw, said the case was so serious it could only be dealt with by a crown court.
Mrs Darwin, who was arrested at Manchester Airport, recently moved to Panama after selling the couple's Teesside home.
She was taken to Hartlepool police station after her return to the UK, where she was questioned by detectives.
It had been thought that Mr Darwin, a former prison officer, had died at sea after the remains of his canoe were found on a beach in Seaton Carew, near Hartlepool, Teesside, in March 2002.
But he turned up at a north London police station on 1 December, claiming he could not remember what had happened to him.