Twenty year-old Niall went into the novel family battle between the Greystones pair as a strong favourite at David Lloyd Riverview last night.
However, Niall had to remain on court for a marathon three hours before prevailing on a 4-6 7-6 (7/5) 6-4 margin.
But an upset materialised in the second men’s singles semi-final when Georgia native Lazare Kukhalashvili overcame number two seed John Morrissey 7-5 6-1 after two hours and one minute.
Kukhalashvili, who is based in Dublin and trains at the Tennis Ireland Centre, finished runner-up to Barry King in last year’s final.
Morrissey, ranked at 30 in the ITF U18 world rankings this year, pushed the Georgian hard in the opener, but Kukhalashvili never looked back after an early break in the second set.
In the women’s singles semi-finals, defending champion Rachael Dillon had to pull out all the stops before getting the better of her Fed Cup teammate Jenny Claffey.
Claffey has recently been largely focussing on her studies at UCD, but she came within a whisker of dumping out Dillon, who is a tennis scholarship student in Tennessee, in a riveting contest.
After losing the first set, Claffey stormed back in magnificent fashion to wrap up the second set without dropping a game. And then in the decider, Dillon was pushed to a tie-break before clinching her place in the decider on a 6-4 0-6 7-6 (9/7) scoreline.
In the final, the top-seeded Donnybrook player will face the number two seed, Sinead Lohan, from Tramore, who ended the title hopes of Naas’s Grainne O’Neill on an emphatic 6-3 6-1 margin after one hour and 39 minutes.