The 53-year-old, who cannot be named to protect the identity of his victims, committed the abuse in Co Donegal and in a European country while on holidays there.
He began abusing one of the children a few weeks after meeting her mother. He would show her child pornography and make her recreate what she had seen.
The now 11-year-old girl said she still worries he will come back and take her and her sister away. She said she “wants to put signs up to let others know what he did”.
The man initially made a full confession but then fled the country while on bail. He was later extradited back to face trial.
He pleaded guilty at the Central Criminal Court to 16 counts of oral rape and sex assault against the two girls between November 2008 and May 2009.
Mr Justice Paul Carney declared him a sex offender and said that the man’s consumption of alcohol or his suicide threat provided no mitigation.
He noted the young age of the victims and the number of offences, before sentencing him to 15 years.
He took into account the man’s remorse and suspended the final three years. Mr Justice Carney also ordered he undergo 18 months post-release supervision and that he have no contact with his victims.
Detective Garda Rosemary Rooney told prosecuting counsel, Isobel Kennedy SC, that the victim’s mother met the accused in an internet chat room and they formed a relationship. He began spending a large amount of time in the family home and would sometimes babysit the children.
He abused the younger child in several locations and would make her watch pornography. He abused the older girl, now 14, in the family home.
He threatened the younger victim that if she told anyone of the abuse he would hit her and she would never see her mother again. In September 2009, she told her family what had been happening and gardaí were alerted.
Shortly afterwards the man gave gardaí a signed confession and said he was “going to do the right thing” and take his own life. He was later arrested and made admissions in interview.
He was released on bail and fled the country until he was extradited back on October 10, 2010.
The elder sister said in her victim impact statement that she felt terrible that she didn’t know he was abusing her younger sister.
“He is a very bad man and I will only feel safe if he is locked away,” she said.
Det Gda Rooney said the man has several previous convictions including serious offences associated with paramilitary activity.
Defence counsel, Paddy McCarthy SC, said his client had been seriously assaulted as a result of the abuse but did not follow up a complaint with gardaí.
He said his client went through a difficult break-up with a former partner and this led him to develop an addiction to internet pornography and to engage in online relationships.