What can birth order tell us about these folks?

Blawgletter has enjoyed re-reading a 1996 book by Frank J. Sulloway –  Born to Rebel:  Birth Order, Family Dynamics, and Creative Lives.  The inside dust jacket says:

At the heart of this pioneering inquiry into human development is a fundamental insight:  that the personalities of siblings vary because they adopt different strategies in the universal quest for parental favor.  Frank J. Sulloway's most important finding is that eldest children identify with parents and authority, and support the status quo, whereas younger children rebel against it.

Only children — singletons — tend to behave more like firstborns than laterborns, according to the book.

Does the finding about the tendency towards conservatism of firstborns/singletons and liberalism of laterborns apply to members of the U.S. Supreme Court?  Mr. Sulloway says yes:

One striking manifestation of this relationship involves the appointment choices of American presidents.  Over the last two centuries, Democratic presidents have shown a consistent tendency to nominate laterborns to the Court.  Republican presidents have manifested the opposite trend.  John F. Kennedy and Lyndon Johnson together made four appointments to the Court.  All four were lastborns.  As a result, the Warren Court eventually boasted 9 laterborn justices and no firstborns. . . . The[] four Republican presidents [who followed Johnson] added 6 firstborns to the Court, out of their 10 available appointments. . . . Relative to firstborn justices, laterborn justices have been significantly more likely to vote in a liberal direction.

But today, 13 years later, does birth order help explain the conservative/liberal leanings of the current justices?  Let's take a look:


        Samuel Alito, Jr.

        Stephen Breyer

        Clarence Thomas (functional; raised with younger brother but separately from older sister)


        Ruth Bader Ginsburg (functional; older sister died very young)

        Antonin Scalia

        David Souter


        Anthony Kennedy

        John Roberts, Jr.


        John Paul Stevens

The Born to Rebel measure nails Alito, Scalia, and Thomas as conservatives; Kennedy as a moderate; and Stevens as a liberal. 

But birth order alone doesn't seem to explain Breyer, Ginsburg, Souter, and Roberts.  What does?  We don't know.  Growing up female (Ginsburg)?  Jewish (Breyer and Ginsburg)?  In San Francisco (Breyer), Massachusetts and New Hampshire (Souter), or upstate New York and Indiana (Roberts)?  As the only brother of an older and two younger sisters (Roberts)?

By the way, Sonia Sotomayor has a younger brother.  Firstborn.  Go figure.