The Northern Ireland Prison Service can confirm the death in custody of a 63-year-old prisoner from Maghaberry Prison.
He died on Monday morning, 25 February.
It is understood to be Liam Adams who had been receiving end-of-life care for terminal cancer in a Belfast hospice.
The 63-year-old was found guilty in 2013 of raping and abusing his daughter, Aine Dahlstrom, and was jailed for 16 years.
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."
Liam Adams began to abuse Ms Dalhstrom, who waived her right to anonymity, when she was just four years old and continued over a six-year period during the 1970s and 1980s.
In 2015, Adams lost an appeal at the High Court against his conviction and sentencing.
g a long extradition battle.