The sons of the canoeist who "returned from the dead" five years after going missing, have been questioned by detectives but are not thought to be part of their parents' suspected insurance fraud, police said on Monday.
Their father, John Darwin, 57, walked into a London police station last week claiming amnesia after apparently drowning at sea in a canoeing accident in 2002.
Police said Darwin had grown a beard and used an assumed name to hide the fact he was still alive.
Darwin appeared in court last week and was charged with obtaining money by deception and making a false declaration to get a passport.
Authorities also charged his wife with two counts of deception. Anne Darwin, 55, is charged with dishonestly obtaining $51,000 and about $250,000 by money transfer in 2003.
Police in northeast England issued a photo of Darwin with a straggly beard and appealed for information from anyone who might have known him under the name John Jones.
Detective Superintendent Tony Hutchinson told reporters she was cooperating with police after returning from Panaman, where she had recently moved.
Hutchinson said there was nothing to suggest the couple's two sons were anything other than victims of the suspected deception, adding that he felt "dreadfully sorry" for them.
"They have believed for the past five years their father is dead," said Hutchinson.
"Now they find out that not only is he alive, but he has been arrested. And they now find out from the newspapers that their mother knew that their father was alive."
The sons said last week they wanted no further contact with their parents.
Hutchinson said the motive for Darwin's reappearance and earlier disappearance remained unknown.
He said Darwin's sons could not identify any event which could have triggered the disappearance, but said police would investigate whether there were financial issues.
International coverage of the case had resulted in several calls to police with information about the couple as well as emails from Spain and the Caribbean, Hutchinson said. He appealed for more information.
Anne Darwin had reported her husband missing when he failed to return home after canoeing in the North Sea. A few weeks later the shattered remains of his red kayak were discovered. He was declared Darwin dead in 2003 after a police inquiry.