England Lions 279 (Westley 84, Foakes 70, Alsop 40, Rashid Khan 4-48) and 210 (Foakes 89*, Gubbins 53, Rashid 8-74) beat Afghanistan 273 (Stanikzai 51, Nabi 51, Roland-Jones 6-73) and 168 (S Curran 3-13, T Curran 3-54) by 48 runs
Curran senior, who had already taken career-best List A figures in the Lions' one-day whitewash against the UAE, claimed three wickets in a fiery new-ball spell to reduce Afghanistan to 27 for 4 as they chased a victory target of 217.
Then Sam took over, adding two more wickets to the one he had taken late on Friday, meaning that when Afghanistan slipped to 54 for 6, all the wickets had gone to the Curran brothers.
Lancashire's Liam Livingstone made the next breakthrough with his leg-spin, Somerset's Jack Leach claimed two wickets both courtesy of smart stumpings from Ben Foakes, and Tom Curran wrapped up the win with a cool catch on the fine leg boundary, fittingly off the bowling of Toby Roland-Jones, the Lions captain, whose six-wicket haul in the first innings had earned a narrow lead.
But Afghanistan made the Lions sweat, with their experienced captain Asghar Stanikzai making 43 from 58 balls, and teenage leg-spin discovery Rashid Khan underlining his all-round ability with 52 from 73 balls to follow 12 wickets on a remarkable first-class debut - until he became the second victim of the Leach-Foakes combination.
"Four-day wins are always the most satisfying," said Tom Curran, still only 21 himself. "We put in a good couple of weeks training prior to this, had a whitewash in the one-day series, and now to top off the trip with a four-day win, the boys are really pleased."
This is Curran's second consecutive Lions trip to the UAE - he also played a starring role in their T20 series victory over Pakistan A in Dubai last December - and he confirmed it had been even more special because he shared it with Sam, who does not turn 20 until next June.
"It's unbelievable," he added. "It's still something I treasure. The journey continues. I'm so proud of him. We're going nicely. I definitely feel a lot more comfortable in this environment. I'm putting in the yards and working hard to do everything I can to be knocking on the doors for England. We'll enjoy the Christmas break and try and come back and do the same in Sri Lanka, if selected."
The Lions play two four-day matches and five one-day matches against Sri Lanka A in February and March, with the squad to be named this week.
"I was just pleased to get a go in my first four-day game for the Lions - that was obviously good experience," Sam Curran said, after ending with impressive figures of 6-1-13-3. "It was also my first time playing with a Kookaburra which was a different experience: different lines, different lengths.
"Swing is probably my strength, but this tour I've learned other ways of bowling on flat wickets, which has been very interesting. I've learned things with Kevin Shine that I probably wouldn't have needed in England. It's nice to know you can play on different wickets."