The famous Quinnell name lives on at Stradey Park after youngster Gavin powered over for the match-winning try in a tense Celtic Cup semi-final on Saturday night.
The Ospreys did the double over their neighbours on the way to winning the Celtic League title, but had no answer to the brute strength of 21-year-old Quinnell. The Scarlets now travel to Dublin next Saturday to play the winners of tonight's (Sunday) second semi-final between Leinster and Munster at Lansdowne Road.
It was a tight affair, with the Ospreys building up a 12-0 lead through the boot of young fly-half Matthew Jones, but they couldn't breach the Scarlets' try-line and the home side slowly but surely took control.
Jones celebrated his call-up to the Wales squad for next month's North American tour with four goals in the opening spell, but the Scarlets had the final say of the half when Lions scrum-half Dwayne Peel took a quick tap and darted into the Ospreys' quarter. The ball was recycled quickly and veteran prop John Davies stormed over the try-line from 10 metres out to narrow the visitors' lead to 12-7 at the break.
Scarlets fly-half Ciaran Thomas made it a two-point game with a penalty goal from the opening move of the second half, before Quinnell came off the bench.
The third of Wales international Derek Quinnell's sons to play at Stradey Park nearly made the perfect entrance, joining a backline move and supplying what should have been a try-scoring pass to winger Tal Selley - if it hadn't been a metre forward. Seconds later, Quinnell burst off the back of a scrum and reached out, but grounded the ball two inches short of the line as the Scarlets searched for a last-gasp route into the Celtic Cup final.
And it came 60 seconds later when Quinnell was given a short pass a metre from the posts. It would have taken a tank to stop him and the Ospreys came up short. Fullback Barry Davies extended the home side's lead with a 53-metre penalty goal and there was no way back for the Ospreys.
Tries - J Davies, G Quinnell
Pens - C Thomas 2, B Davies
Cons - C Thomas 2
Pens - M Jones 5
Halftime: Ospreys 12-7
Yellow Card: B Cockbain (Ospreys)
Referee: Donal Courtney (Ireland)