Sinn Fein president Gerry Adams revealed his late father subjected family members to emotional, physical and sexual abuse.
He said his father was in denial for many years about his actions and eventually died a lonely old man.
In an interview with RTE News, Mr Adams also called on his brother, Liam, to give himself up to the authorities.
Liam Adams is wanted by the PSNI over charges of abuse against his daughter over a period of several years during her childhood.
Gerry Adams urged his brother to go to the PSNI for the sake of his niece Aine, Liam's daughter, who has waived her right to anonymity.
"I was almost 50-years-old and up to that point I thought we were like any other family with a loving father," he said.
"It was a deep shock."
Mr Adams said he had no recollection of being abused. He appealed for his brother to come forward and hand himself over to police.
"Aine (Tyrell, Liam's daughter) needs justice. This has gone on for far too long. And the only way now she can get justice is through the courts," he said.
"And Liam, for her sake especially, for his sake and for the sake of his other children, should do that. He should come forward."
He was asked about knowing of the alleged crimes for the past 22 years but said it went on for too long and it was Liam's fault it went on for too long.
"More important to me, Aine and her mother had to deal with all of this," he added.
"But in the course of trying to deal with it I also discovered my father was an abuser.
"I don't want to distract for one second from Aine's plight. I have felt for some long time we should go public about my father as part of the healing process within my own family and to try and help other families who are in the same predicament."
The family received professional help.
"Those who were abused didn't want to go to the police about it so in a very difficult way with everybody coming at this at different speeds and with everybody coming at it from slightly different perspectives we have with the assistance of professionals, with the assistance of other family members and friends, we have been able to survive it," he added.
He said his father was in denial for a lot of that time.
There were 13 children, 10 survived and three died at birth or shortly after.
"He ended up dying a very lonely man where he should have been surrounded by loving family members," he said.
"I myself for a long time wanted this to be publicised because there is a culture of concealment. But we can only do this when everybody is strong enough to do it.
"And we don't do it for any other reason than a necessary step in the healing process in our own clan. And also other families who are in the same predicament or individuals who just feel this is the end of the world."
He said it was not the end of the world.
"It obviously tests your faith in humanity when an iconic figure like my father engages in the psychological and emotional and physical and sexual abuse of a child, of his child," he added.
"But with attention, with understanding, with resolve, and with love we can find our way through all of this."
He was asked about his father's republican funeral and tricolour on his coffin.
"Personally that was one of the great dilemmas for me because I'm a republican. I'm speaking here as a human being, as a family member," he said.
"I didn't want him buried with the tricolour. I think he besmirched it but it was a dilemma for other members of my family who felt that they didn't want this at that time out in the open."
Had he not been buried as a former republican activist in the 1930s, a former prisoner, that would have drawn attention to the fact that there was something wrong.
"So you have to look after the living as opposed to the dead," he said.
I always also had a view that it was going to come out at some time."
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