Whilst the U18 went down 27-14 to the Blues at Pontypridd's Sardis Road, the U16 came through 13-0 against last season's champions the Scarlets.
Full back Ieuan Coombs and blindside flanker James Thomas bagged tries for the Dragons with Danny Ellis adding a penalty for good measure. However, it was the outstanding second half defence from the likes of centre Adam Hughes that proved the big difference for the Dragons.
The U18 mustered two tries in the game at Pontypridd - from wing Anthony Brown and replacement scrum half James Leadbeater, but the Blues helped themselves to four as their greater strength and stature at forward came through. David Langdon, so prolific with the boot last season, added two conversions for the Dragons.
The Ospreys made the perfect start to their season - winning both games at U18 and U16 levels. Having lost out to the Scarlets in last season's final at the Millennium Stadium, the U18 were desperate to seek revenge against the Scarlets at Aberavon's Talbot Athletic Ground. And despite being led on two seperate occasions in the game, the Ospreys came through to edge a thrilling contest 31-26.
John Jones, Lloyd Elliott and Tom Williams (2) crossed for tries for the Ospreys whilst John Davies ran in a brace for the Scarlets and Daniel Evans and Rhys Williams helped themselves to singles. Evans added three conversions for the visitors, who had tight head prop Ryan Foreshaw red carded, but two penalties and a conversions from Richard Cunniffe and a third penalty, from Lee Halfpenny, edged the Ospreys home in a game regional rugby director Dai Arthur described as hugely entertaining.
The Ospreys U16 proved too strong for Blues South at Llanrumney Field in Cardiff where replacement wing Brett Pritchard suffered the worst possible start to his season by breaking an ankle. However, before that, Jason Jones, Rhys Roberts and Rory Pitman crossed for tries with Daniel Biggar, in his second season with the side, converting one.
Ryan Moore hit back after half time with a try for the Blues, but the home side was unable to close the gap any further as the Ospreys ran out 17-5 winners.