The brothers joked and hugged at the start of the match but things turned serious when a destructive opening stand of 142 between Wriddhiman Saha (81) and Shubman Gill (94 not out) powered Gujarat to their highest ever IPL total of 227-2.
Madhwal then returned figures of 5-5 to dismiss Lucknow for 101 as Mumbai booked a meeting with holders and regular season table-toppers Gujarat in the next play-off encounter on Friday. The winners of that clash will meet Chennai in the final on Sunday.
Nicholas Pooran's 58 guided Lucknow to 176-8, a total that was threatened by Rinku, a left-hand batsman, who smashed four sixes in his 33-ball knock but Kolkata ended on 175-7.
Mohsin Khan held his nerve to defend 11 runs off the final over as Lucknow Super Giants beat Mumbai Indians by five runs on Tuesday to move one step closer to the knockouts in the Indian Premier League.
Rahul, playing his 100th Indian Premier League match, steered Lucknow to 199 for four after being put into bat first at Mumbai's Brabourne Stadium.
Chasing 178 for victory, Rajasthan were in trouble at 55-4 when Samson and the left-handed Hetmyer turned on the chase at the world's biggest cricket stadium in Ahmedabad.
Skipper K.L. Rahul and left-arm spin all-rounder Krunal Pandya shared a 55-run partnership off 38 balls for the third wicket to lead Lucknow Super Giants to a comfortable five-wicket victory over Sunrisers Hyderabad.
Lucknow Super Giants were 37/3 chasing RCB's 213 but Marcus Stoinis brought Lucknow back with his impressive 30-ball 65 while Nicholas Pooran smashed a sensational 19-ball 62 to take the team to a last-ball thrilling one-wicket victory on Monday.
Marcus Stoinis and Avesh Khan shared five wickets between them as Lucknow Super Kings defended 154 to defeat Rajasthan Royals by 10 runs in the Indian Premier League on Wednesday.