So you haven’t heard enough about brothers Peyton and Eli Manning — their quarterbacking careers, their Super Bowl MVP awards and their skills as Madison Avenue pitchmen?

Let’s analyze the effects of their birth order. No statistics, just a bit of scholarly speculation as Eli prepares to lead the New York Giants into Super Bowl XLVI on Feb. 5 against the New England Patriots.

Peyton will turn 36 in March, and Eli just turned 31. Then there is their big brother, Cooper, 37, whose career as a wide receiver at the University of Mississippi ended before it began because of spinal stenosis.

A student of birth order like Frank J. Sulloway, a psychology professor at the University of California, Berkeley, says that first-born children tend to be conscientious, responsible, reliable and achievement-oriented, while later-born children can be rebellious, easygoing, excitement-seeking and risk-taking. Indeed, as later-born children, Eli and Peyton should be more alike than different.

Sulloway also said that siblings born within five years of each other can be so competitive that they do not play the same sports — or if they do, they play different positions. Yet, here are Eli and Peyton, both elite quarterbacks, born less than five years apart, acting close and loving and barely competitive.

Peyton is protective of Eli, as an older brother often is. Rather than beat each other bloody, they respect each other. We can only imagine the wedgies Peyton perpetrated on Eli in their youth.

But why do Peyton and Eli seem more like buddies than brothers angling as grown men to be Daddy’s favorite? Sulloway suggested that Manning family dynamics — where their father, Archie, and mother, Olivia, supported their sons, and Peyton supported Eli without making him miserable — might be the reason.

“An elder sibling can play the role of a surrogate parent,” said Sulloway, the author of “Born to Rebel: Birth Order, Family Dynamics, and Creative Lives.”

He added, “Maybe when Cooper dropped out, Peyton might have felt more protective of Eli.”

Cooper did not drop out of the Manning family — he left its domain of football princelings. But his condition could have skewed Manning family birth order analysis. Had Cooper been the first Manning son into the NFL, he might have exhibited the more conservative traits that first-borns in studies tend to show. But with Cooper out of the pigskin picture, Peyton would be the de facto first-born.

“You can get what’s called a functional first-born, someone who rises to the office when the chronological first-born can’t discharge the responsibilities of the first-born,” said Jeffrey Kluger, the author of “The Sibling Effect: What the Bonds Among Brothers and Sisters Reveal About Us.”

Yes, this is armchair fraternal analysis. Is Peyton really the more conservative quarterback? Is Eli the wild one? Does Peyton avoid the pressure that Eli must often escape because of a quicker release and a stouter offensive line? There are no simple answers. Each has different athletic skills and genetic set-ups.

They play for different coaches in different systems, and they work in different home stadiums.

But Kluger said that Eli’s ability to cope with being frequently knocked down and sacked last Sunday against San Francisco was evidence that he was the more aggressive Manning. “Eli throws himself around a bit more,” he said. “We’ve seen Peyton knocked around, but this is more consistent with Eli.”

If the three Mannings clung stiffly to birth order analysis, Eli would be the most sociable, outgoing one. Yet, that role is publicly played by Peyton, who is more quotable and is one of sports’ endorsement kings. Still, was he demonstrating a teeny bit of risk avoidance in a MasterCard commercial where he cheered on a deli worker slicing cold cuts to “Cut that meat!” rather than working the slicer himself?

In Eli’s commercials, he acts more reserved and is less natural. Indeed, Cooper, an energy trader, subverts the standard tendencies of birth order by being considered the family cut-up.

“Cooper as the class clown is not typical of first-born,” Sulloway said. “That would have changed the available niches in the family. Do you want to be the second-best class clown in the family?”