Alan Bennett, brother of Brady victim Keith, has posted on the website dedicated to the search for Keith Moors grave.
On searchingforkeith.com Alan said:
The lawyer for Winnie Johnson, John Ainley, has said that his client's family is treating recent developments "with some suspicion".
He told ITV News it was "very timely" that the documentary which brought the letter claim to light is due to be aired tomorrow.
A solicitor who used to represent Winnie Johnson, Keith Bennett's mother, has described the latest development as "extremely interesting and exciting".
David Kirwan, a managing partner with Kirwans law firm, said he had a series of face-to-face meetings with Ian Brady at Ashworth mental hospital in 2007. He said:
This photograph shows Jackie Powell, Ian Brady's mental health advocate, who has claimed that Brady gave her a sealed envelope addressed to the mother of one of his victims.
The revelation raised hopes that the envelope may contain the location of Keith Bennett, the only one of Brady's victims whose body has not been found.
Ms Powell says she no longer has the envelope and that her words have been "misrepresented". Greater Manchester Police are investigating.
The lawyer for Winnie Johnson, John Ainley, has said he is not "holding his breath" that recent developments will lead to the location of her son's body.
He told Sky News: "It may be at this late stage that he [Ian Brady] has got some sort of conscience about all of this" but he said that he would be surprised.
Mr Ainley added that Ms Johnson's family is "reassured that the police are investigating" but that he did not think its was advisable to raise her expectations.
No new date has been set for Ian Brady's mental health tribunal.
It is understood that arrangements need to be put in place to agree on a suitable date for all legal parties in the case.
Brady is challenging his insanity diagnosis which allows doctors at Ashworthmental hospital in Merseyside to force feed him. It is believed he wants to return to the normal prison system where staff would not be allowed to stop him going on hunger strike.
Attention is focussing on Ian Brady's mental health advocate, Jackie Powell, who has claimed in a television documentary that he wrote a letter to the mother of one of his victims.
A mental health advocate is not the same as a lawyer. Their role, as defined by the Department for Health, is as follows:
Winnie Johnson's lawyer, John Ainley, has said he is "sceptical" about the apparent revelation of a letter from Ian Brady:
Greater Manchester Police have no immediate plans to search Saddleworth Moor, near Manchester, where he and Myra Hindley buried four of their five victims.