Tom Curran's bowling figures - 1 for 55 in four overs - in Friday night's game against South Africa were the sixth-most expensive in England's T20I history. But at least none of the five men above him in that list had to walk off alongside their grinning brother after he had taken three cheap wickets.

"Tom's very competitive and is a relaxed guy, so he'll move on pretty quickly," Sam said after England's five-wicket win. "T20 is a very strange game. You can bowl well and still get hit for a lot of runs, and you can bowl badly and get loads of wickets."

But in truth, Sam bowled well, and Tom bowled poorly. While Sam managed to disguise his variations, change his lengths and nail a hard length, Tom was taken to pieces in his second over by Faf du Plessis and ended up leaking 24 runs as he strayed into the slot.

The upshot is that if England decide to inject Mark Wood's pace in Sunday's game at Paarl, it is likely to be Tom rather than Sam that makes way. If that seems unsurprising, it is evidence of the effect that the IPL has had on Sam's reputation as a T20 player: Friday night was only his sixth T20I appearance and his first in over a year.

It is quite a reversal. While Sam's first exposure to professional cricket was in Surrey's T20 Blast side, he has generally been considered to be the slightly better red-ball cricketer, while Tom was ahead of him in the white-ball pecking order. Now, Tom has not played a first-class game since April 2019, and is arguably a less attractive proposition in limited-overs cricket, too.

That is not to say that he has undergone any major decline. Eoin Morgan, England's white-ball captain, evidently has faith in him, deciding to give him two powerplay overs and continuing to back him at the death even after du Plessis' onslaught.

It is worth noting, too, that he spent much of the IPL sitting on the Rajasthan Royals bench, so was not match-fresh in the way most of his team-mates were. He will return to the Big Bash League with Sydney Sixers after this tour, for whom he has played some of his best cricket, and is likely to remain very much in the England reckoning.

In contrast, Sam - in recognition of his lengthy stints in the biosecure bubbles this summer - will return home after the T20I leg of this tour is complete. That speaks volumes of the strides he has made and his importance to the England set-up across formats. He received glowing reviews during his time at the IPL with the Chennai Super Kings - captain MS Dhoni labelled him "a complete cricketer" - and said that he had taken his game to "a different standard" at the tournament.

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While his bowling caught the eye in Friday's series opener, Sam's three-ball innings with the bat was just as entertaining. After being hit on the grille by a Lungi Ngidi bouncer, the first ball he faced, he lined up Kagiso Rabada to smite his second for six over long-on - evidence, perhaps, of his mischievous streak.

That Sam has caught up with Tom so quickly should not come as a surprise: tennis fans, for example, will note the relative successes of the Williams and Murray siblings (in both families, the younger sibling is the superstar). There is a sociological explanation for 'the sibling effect', in which younger siblings enjoy more success than their older siblings, rooted in their early exposure to regular sport, the need to keep up, and psychological rivalry. As Tim Wigmore and Mark Williams write in their book The Best: How Elite Athletes are Made: "If you have a younger sibling, they are probably better at sport than you are."

That seems to fit in the example of the Currans: Sam's emergence as a T20 allrounder puts his brother's England place in jeopardy. When Jofra Archer has been unavailable through injury or rest, Morgan has backed Tom Curran and Chris Jordan as their death-overs specialists, but Archer's presence in this series means both seamers need to prove their versatility.

With Wood - or Reece Topley, the tall left-armer who last played a T20I in the 2016 T20 World Cup - in contention as England look for extra pace with the new ball, there may well be room for only one Curran in this side. Sam's advantage with the bat and his new-found ability to bowl in all three phases of an innings means that Tom finds himself looking over his shoulder.