Connor McNealis, 27, was given a six-year sentence in April 2024 after being found guilty following a trial at the High Court in Edinburgh.
The Crown Office and Procurator Fiscal Service asked the court to consider imposing a longer custodial term due to the serious nature of the offences.
The Appeal Court upheld the Crown appeal. The original sentence has been quashed and replaced with a nine-year custodial term.
While sentence is rightfully the domain of the independent judiciary, the balance of justice is served by the Crown being allowed to appeal in limited circumstances.
The Appeal Court has set a high test to be satisfied for this to happen.
The sentence must be unduly lenient, meaning it falls outside the range of sentences which the judge could reasonably have considered appropriate having taken account of all relevant factors.
Kenny Donnelly, Deputy Crown Agent for the Crown Office and Procurator Fiscal Service, said:
“COPFS is committed to improving the criminal justice journey for victims, from the stage of reporting all the way through to sentencing.
“Prosecutors have a responsibility in legislation to consider appeals based upon undue leniency in sentencing.
"Such appeals are rare but important to ensure the public interest is properly served.
"They allow the court to review sentences that the Crown believe fall outside the range of punishment reasonably considered appropriate.
"COPFS believes that it is important that the harm caused by sexual offending, and the culpability of the convicted person, must be consistently reflected in sentencing decisions.”
McNealis was 19-years-old when he attacked and raped the first young woman on two separate occasions in 2016.
He was 23 and 24 when he raped the second victim on various occasions in 2020 and 2021.
His offending took place in the Edinburgh and Paisley areas.