There is a claim in Papua New Guinea that Arthur Somare misled the public when he announced that the prime minister's family wished Sir Michael Somare's retirement from politics because of ill-health.
The claim has been made by John Aramura, who is the brother of Sir Michael's wife, Lady Veronica Somare.
Mr Aramura has told the Post Courier that his sister, who is in Singapore with Sir Michael, is unhappy with her son's announcement.
Mr Aramura says according to Lady Veronica, the family discussions are not in line with what Arthur has done.
He says by custom and tradition, Arthur Somare is only the third born in the family and did not have any authority, or standing as a chief or leader, to make such statements.
Mr Aramura's comment has been supported by the traditional chiefs and leaders of East Sepik, where Sir Michael has been elected.
A joint statement, signed by the nine chiefs of East Sepik, says what Arthur Somare has done is shameful and of total ignorance of family and traditional values.
Arthur Somare, who is the Minister of Public Enterprises, will face a leadership tribunal on Monday on allegations of misconduct in office.