The Risers found it hard from the start after winning the toss and electing to bat first.
Delbert Gayle (27) and Nicholas Lewin (15 not out) were the only batsmen to reach double figures as pacers Ojay Shields (2-9 off two overs) and Andel Gordon (2-13 off two) combined to restrict the Risers to a modest 72-6 off their 10 overs.
Jamaica Scorpions all-rounder Alwyn Williams with 30 not out and Damani Sewell with 15 not out then helped the Stars reach 71-1 in the eighth over before rain ended proceedings with the Stars comfortably 19 runs ahead of the Duckworth/Lewis par score.
West Indies opener John Campbell earlier made 20 for the Stars who now have four wins from eight matches.
Asking the Stars to bat first after winning the toss, the Warriors had early success after removing West Indies opener John Campbell for 14.
Sashane Anderson (22) and Suwayne Wilson (12) were the only other Stars batsmen to reach double figures as Frew, a member of the West Indies U-19 World Cup winning squad in 2016, ripped through the batting line-up to finish with figures of 4-16 from his two overs.
In the end, the Stars were restricted to a modest 81-7 off their 10 overs.
The Warriors made light work of the chase, reaching 83-3 off 8.4 overs to get their second win of the competition.
They got home thanks to some indiscipline from the Stars bowlers and solid showings from Ockeeno Farqharson (21), Jevoy Spence (15) and Andre McCarthy (13 not out).
West Indies U-19 representative Andel Gordon took 2-11 off his two overs.
After the United Stars won the toss and elected to field, they bowled well to restrict the Titans to 81-8 off their 10 overs.
Sherdon Allen (36) and Oshane Walters (10) were the only Titans batsmen to reach double figures as West Indies U-19 representative Andel Gordon led the United Stars bowling with 3-10 off his two overs.
Dwayne Hamilton also took 2-21 for the United Stars.
The Stars reply never got out of first gear as only Jamaica Scorpions all-rounder Alwyn Williams was able to get to double figures with 16.
At the time the rain came down, the United Stars were teetering at 41-7 off 7 overs. There was no further play as the match was then called off with the Stars 18 runs short of their target via the Duckworth-Lewis method.
The aforementioned Grant produced an excellent spell of bowling, taking 4-9 off his two overs.
After winning the toss and choosing to field first, the Kings were in good form with the ball, holding the United Stars to a modest 82-6 in their 10 overs.
Jamaica Scorpions player, Alwyn Williams, was the only batsman to make a significant contribution for the Stars with 35 against 3-13 off two overs from medium-pacer Oraine Williams and 2-5 off one over from leg-spinner Kenroy Williams.
When it came time for the Kings to chase, McCarthy, batting at number four, was the chief destroyer with his 39 coming off just 12 balls including two fours and four sixes.
Opener Kennar Lewis also contributed 19 as the Kings easily chased their target reaching 83-3 off just 5.3 overs.
Left-arm quick Andel Gordon was the best bowler for the United Stars with 2-21 from his two overs.
The Surrey Kings now have five wins in five games, living up to their tag as favourites.
This was the second agonizing one-wicket defeat in the series, following a similar result on the second Youth ODI in Beckenham.
Left-arm quick Gordon, who claimed 3 for 37, stood out bowling with good pace and swing, highlighted by his dismissal of England opener William Luxton, clean bowled in the first over. He was well supported by his right-arm pace duo compatriots Layne, 3 for 40, and Isai Thorne, 2 for 40, as they kept West Indies in the contest by regularly taking wickets.
When Layne dismissed tail end batters Nathan Barnwell caught behind and Joshua Boyden comprehensively bowled in the space of two overs, West Indies were on the verge of pulling off a thrilling fightback win with England still needing 12 runs. However, George Bell, who had an unbeaten half-century of 60 from 115 balls, held his nerve alongside the number 11 batter Sonny Baker to take the home side over the line.
Earlier, Matthew Nandu (51) became the second West Indies batsman to score a half-century on tour alongside Teddy Bishop. His 57-run third-wicket partnership with Ackeem Auguste 32 had West Indies solidly placed at one stage on 101 for 2. But the innings never kicked on, with captain on the day Giovonte Depeiza (34) being the only other major contributor.
The two teams will return to the same venue on Friday for the series finale. First ball is 10:30 am (5:30 Eastern Caribbean/4:30 am Jamaica).
