The death has taken place of convicted paedophile Liam Adams, whose prosecution six years ago drew his brother Sinn Féin TD Gerry Adams into political controversy.
Liam Adams (63) had been receiving palliative care for terminal cancer in a Belfast hospice.
He was found guilty in 2013 of raping and abusing his daughter, Aine Dahlstrom between the ages of four and nine, and was jailed for 16 years. He was moved to the medical facility earlier this year for end-of-life care.
A statement from the Northern Ireland Prison Service confirmed the death in custody of an inmate from Maghaberry Prison.
“The prisoner died on Monday morning, February 25th. His next of kin have been informed.
“As with standard procedure, the PSNI and Prisoner Ombudsman have been informed.”
Ronnie Armour, Head of the Northern Ireland Prison Service, said: "I would like to extend my sympathy to the family of the prisoner. My thoughts are with them at this difficult time."
Adams, a former youth worker and also a former IRA member, was convicted of 10 offences — three counts of rape, four of indecent assault and three of gross indecency. In 2015, Adams lost an appeal at the High Court against his conviction and sentencing.
The offences occurred between 1977 and 1983, when Adams was aged between 22 and 26.
Former Sinn Féin president Gerry Adams gave evidence at his brother’s first trial — which collapsed in April 2013 for legal reasons.
During the 2013 trial, Mr Adams told the court that in 2000, during a walk in the rain in Dundalk, his brother had admitted sexually abusing his daughter,
Mr Adams made his first report to police about the allegations in 2007 shortly after his party voted to accept the PSNI, but did not tell officers about the confession until 2009, when he made a second statement.
Mr Adams was criticised for not informing police about the confession at an earlier date.
In 2015, the Northern Ireland Police Ombudsman found that police were not politically motivated when they said Gerry Adams should not be prosecuted for allegedly withholding information about his paedophile brother.
The police watchdog said there was no evidence of misconduct, or that officers had been influenced by the former Sinn Féin president’s status. – Additional reporting: PA