Boult is the younger, 25, by a few days short of a year, although both were teammates in the New Zealand U19 team, with Kane Williamson and Corey Anderson.
Boult made his test debut more than three years after Southee and his ODI debut four years later.
"We've played a lot of cricket together going back to age-group stuff and NZ A and domestic and now international level," Southee said in Melbourne yesterday.
"We've played a lot of test cricket together, haven't played a lot of one-day cricket leading up to this World Cup, and Trent hadn't played a lot of one-day cricket leading up to this.
"But he's proved himself on the international stage in test and T20 cricket so it was a matter of time before he became a more permanent fixture in the one-day side.
"He's grown another leg and to do what he's done in the last couple of months is amazing."
Southee has the ear of captain Brendon McCullum and is one of the team's on- and off-field leaders. If we were going to go all DC Comics on this, Southee is Batman, Boult is Robin.
But over the course of this World Cup he has lost his primacy to Boult - when Commissioner McCullum needs to rid Gotham of a pest, he's calling on Robin first.
Boult and Southee are close, they enjoy each other's success, but you can guarantee that on a subliminal level at least, it will be gnawing away at Southee that his junior partner has gone gangbusters while his performances have tailed off after the spectacular 7-33 that blew the English out of Wellington.
"It's great to bowl alongside him knowing you have someone to rely on at the other end to do a great job and who is going keep pressure on the batsmen. We have a great partnership and good friendship off the field as well, so I can't express how proud I am at what he's done over the last couple of months."
Breaking Southee's World Cup down, there is a distinct before-and-after feel to his tournament. Before Australia at Eden Park, he was peerless, with 11 wickets in three games; after Australia, where he took 2-65 off nine overs (which is perfectly fine until you consider that accounted for 43 per cent of all Australia's runs), he has been close to toothless, with just two wickets against the West Indies to show for it.
There were signs of improvement against South Africa. Sure, David Miller brutalised him late but there was a case for that one; Southee wasn't on the same page as his captain. He had mid-off inside the circle and persisted in bowling full outside off stump to the left-hander, suggesting it could have been a tactical error as much as a skills mistake.
In a chance encounter with a former New Zealand fast bowler this week, he mentioned that he felt Southee has started bowling "along" the pitch and had almost been seduced by the prospect of late swing. He wanted him to get taller at the crease and get a little more direct.
Southee maintains this attack is still effective, even when the ball is not swerving around corners.
"We have found ways to take wickets when it's not swinging, that's the beauty of our attack," he said.
"We've got variety to it and if it does swing we do become a bit more dangerous."
Whatever the mechanics of Southee's action, this much is true: how he and Boult perform with the new ball(s) will go a long way to determining the result of the final.
Now would be a good time for Southee to rediscover his magic - for the bacon to jump back on the plate with the eggs.
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