The 53-year-old, who cannot be identified for legal reasons, had pleaded not guilty at the Central Criminal Court to two counts of rape and two counts of indecent assault against his sister-in-law on dates between 1985 and 1986.
A jury found him guilty on all counts and he was given a suspended seven-year term by Mr Justice Garrett Sheehan on June 7, 2013.
In suspending the term, Mr Justice Sheehan had said the man’s family needed support and care. Two of his young sons had autism and required 24-hour care.
The DPP successful applied for a review of the man’s sentence earlier this month on grounds that it was “unduly lenient”.
In imposing a three-year term, President of the Court of Appeal Mr Justice Seán Ryan said the object of the court was “just punishment” — punishment that is just.
He was 25 at the time of the attacks, while his victim was 13, going on 14. The offences occurred in a spare bedroom of the home on occasions when the complainant was staying over in the house.