Henry and Robbie, both members of the Kiwi team that clinched the series at Bolton on Saturday, were last night's subjects in Family Affairs on Radio 5 Live - a sort of In the Psychiatrist's chair for sporting relatives.
The timing is good, because, as the interviews reveal, this is the first time that Robbie, the younger by two years, has been able to claim any seniority over his brother.
He is the one starting the Test matches, while Henry must wait to come on as a substitute. According to Prof Jenny Cozens, the usual balance of the relationship between the two is very different.
"The psychology of the relationship between these two seems to me to be governed by the central tenet in any power relationship," says Prof Cozens. "That is, those who have less power watch carefully those in close relation to them who have more power. So workers know more about bosses, traditional wives about husbands and younger siblings about older ones."
Prof Cozens describes the relationship as one of "somewhat one-way interest". This is Robbie on how he reads his brother: "I think me and Henry could play well on the field and not need to speak to each other very much - a little communication with looks. I know when my brother is pissed off with me, I know when he is angry with me. You've just got to look in his eyes."
Prof Cozens says that it is, "very important for a junior member of a partnership to know what angers the senior partner. Robbie follows this pattern."
Robbie elaborates on the same theme. "He hardly ever came to any of my games and I will tell you that now," he says. "I went to all his home games. He hardly went to any of mine."
Prof Cozens observes: "They may laugh and joke about it now, but I believe Henry wasn't as interested in watching Robbie as Robbie was in watching him."
In the programme, the brothers recall a match in which they played against each other, Robbie for Bradford and Henry for Wigan.
"Robbie's recollection of what happened is more precise and clear than Henry's. However, just because the power relationship is unequal, it doesn't mean Henry is indifferent to Robbie. He's not - and mentions Robbie as one of Bradford's best players - but it is Robbie who can recall the detail because he has been watching and following Henry all his life. Henry may be generous in his praise, but he is clearly not threatened by Robbie at all."
The programme also reveals that Robbie was frequently mistaken for Henry by other Kiwi players when he first joined the squad. The brothers also credit a mixture of nature and nurture for giving them the extravagant talent they share.
"I think we had the right gene make-up," says Robbie. "Thanks to mum and dad, we had a quick pair of feet that could get us out of trouble."
Henry, however, stresses the practical help their parents provided. "They were working-class people but they did everything for us."
There have been two major developments since the interviews with the brothers were taped. The first is their success together in a New Zealand side which many thought could not accommodate both of them.
The second is that Henry has signed to play alongside Robbie at Bradford next season - another situation in which the younger brother will have a form of seniority.
Prof Cozens says that this will, in effect, fulfil what Robbie wanted as a youngster. "I suspect Robbie... would like to have been more involved with Henry... In an ideal world, he'd like to be on the same team as Henry."
Robbie agrees: "I would love it. I think there's no one in the competition who knows my brother as well as I do, because of those natural things you see as a youth growing up."
In the third Test at Watford on Saturday, but especially for Bradford next season, that theory will be tried out.
Prof Cozens sees no psychological barrier to the relationship thriving on the pitch as well as off.
"I believe they would make a formidable pairing in the same team," she concludes.Reuse content