Gerry Adams came under fresh pressure after a Sunday newspaper claimed his suspected paedophile brother was Sinn Fein's most senior official in Co Louth.
Liam Adams chaired an IRA commemoration in the Irish Republic border county in November 1997 over a year after the Sinn Fein president claimed to have moved immediately to have him expelled from the party, a report in the Sunday Tribune said.
Liam introduced the main speaker, Sinn Fein national chairman Mitchel McLaughlin, with the event reported in a local paper.
Sinn Fein denied claims of a cover-up and said it had already admitted he was a member of the party for a short period in the 1990s.
Liam Adams is wanted by the PSNI on charges of repeatedly raping his daughter Aine Tyrell from the age of four but denies the allegation. He handed himself in to police in the Republic before Christmas after his brother appealed for him to answer the charge.
According to the Tribune, Liam Adams was chairman of the Louth comhairle ceantair, liaising directly with the national Sinn Fein leadership.
In June 1996 he welcomed Martin McGuinness to Dundalk and stood beside him at the official opening of the party's new office in the town. In a local paper he is photographed cutting the ribbon with McGuinness.
He also chaired the 40th anniversary commemoration at Edentubber for five IRA men killed in the Border campaign. After Bodenstown it is the most significant individual commemoration in the republican calendar.
A Sinn Fein spokesman said: "It was Sinn Fein who stated that Liam Adams was a member of the party for a short time during the 1990s which (undermines) any notion of a cover up."
He said Gerry Adams made clear that when he found out Liam Adams was a party member he moved to have him dumped and claimed dissident republicans were inspiring the latest revelations.