Oli Cooper, the teenage son of former Cardiff City, Wimbledon and Wolves player and coach Kevin, sent the Bluebirds crashing out of the FAW Youth Cup at Llanelli’s Stebonheath Park stadium.
Cooper, aged 19, struck just before half-time in in fiercely contested semi-final, earning the Swans a 1-0 win..
The young Bluebirds had scored 38 goals in three ties on their way to the last four, but Swansea goalkeeper Nathan Shepperd and his defence kept a clean sheet.
Swansea will play Cardiff Met or The New Saints, who play their semi-final at Latham Park, Newton on Sunday March 10 (2pm).
The Swans have won the Welsh Youth Cup in nine successive seasons, beating Cardiff on penalties in the 2018 final, and are on course to make it 10.
Cooper went close after only three minutes when his shoot hit a post, while he did well to chip goalkeeper George Ratcliffe on six minutes. Defender Joel Bagan chase back to head the ball over Cardiff’s bar.
Mason Jones-Thomas burst clear, one-on-one with Ratcliffe, after 22 minutes. The Bluebirds ‘keeper saved superbly.
Dan Griffiths, Cardiff’s top scorer, was stopped by Ben Cabango on his way towards goal, while his overhead kick flew just over the bar.
Keenan Patten went for goal from long range and that wasn’t far off before Cooper scored the only goal from close range after 44 minutes.
In a close fought second half the young Bluebirds worked to create chances, but Swansea goalkeeper Shepperd maintained his clean sheet.
Cardiff are still chasing a trophy. They are top of the Professional Development Under-18 League South table.
Cardiff City: George Ratcliffe, Laurence Wootton, Dan Martin (Kieron Evans 57), Ben Margetson (Isaak Davies 57), Ryan Reynolds, Joel Bagan, Keenan Patten, Makin, Sam Bowen, Dan Griffiths, Sion Spence, Bolger. Subs not used: Jordan Duffey, Harry Pinchard, Jac Davies.
Swansea City: Nathan Shepperd, Cameron Evans (Simone Paulet 62), Matthew Blake, Kees de Boer (William Rickard 79), Brandon Cooper, Ben Cabango, Tivongo Rushesha, Tom Price, Mason Jones-Thomas, Cameron Berry, Oli Cooper. Subs not used: Jack Withers, Jayden Reid, Scott Reed (gk).
Cardiff’s remaining Professional Development Under-18 League fixtures:
Saturday 9 v Nottingham Forest (home at Cardiff International Sports Campus, Leckwith, Noon)
Saturday 16 v Leeds United (away, 11am)
Saturday 23 v Bolton Wanderers (away, 11am)
Saturday 30 v Sheffield Wednesday (home at Cardiff International Sports Campus, Leckwith, 11am)
Saturday 6 v Crewe Alexandra (away, 11am)
Saturday 13 v Burnley (home at Cardiff International Sports Campus, Leckwith, 11am)