Liam Adams is facing 18 charges in connection with the alleged abuse of his daughter Áine Tyrell.
Speaking on RTÉ Radio's 'This Week', Gerry Adams said he had not spoken to his brother in two years, and described the ongoing controversy as 'dreadful' and 'difficult'.
He added that a lot of families were dealing with similar problems.
Speaking on the same programme, Mr Adams repeated his criticism of the Government's handling of the economic crisis, but did not categorically rule out going into power with Fianna Fáil after the next General Election.
He said Sinn Fein's proposal to introduce a solidarity tax on assets worth more than €1m, excluding farm land, would yield €3bn.
He said this would help fund a stimulus package, which would cost the State €3.2bn.
