Type A (Functional only born): Only child of your gender born within five years both ways (overrides B)
Type B (Functional first born): Oldest of your gender (overrides D)
Type C (Functional last born): Youngest of your gender (overrides D)
Type D (Functional middle born): Middle child
To pique your interest:
- Most pastors, politicians, and architects are functional firstborns or only children.
- Most comedians and salespeople are functional youngest children.
- Most psychologists and writers are middle children.
And, finally, just for Flatfingers:
Middles and youngest children are more likely to be Idealists/Socializers or Artisians/Killers.
Firstborns and only children are more likely to be Rationals/Explorers or Guardians/Achievers.
Also, if you like this sort of thing, you might want to check out Kevin Leman's The Birth Order Book.
From the book:
In reality it's a little more complicated than this - having a single younger sibling of the opposite gender can make you either a functional only or a functional firstborn, for instance, and there's a vast variety of other ways your personality can develop... but I'm putting it this way to keep it simple.First: perfectionist, reliable, conscientious, a list maker, well organized, hard driving, a natural leader, critical, serious, scholarly, logical, doesn’t like surprises, a techie
Middle: mediator, compromising, diplomatic, avoids conflict, independent, loyal to peers, has many friends, a maverick, secretive, used to not having attention
Last: manipulative, charming, blames others, attention seeker, tenacious, people person, natural salesperson, precocious, engaging, affectionate, loves surprises
Only: little adult by age seven, very thorough, deliberate, high achiever, self-motivated, fearful, cautious, voracious reader, black-and-white thinker, talks in extremes, can’t bear to fail, has very high expectations for self, more comfortable with people who are older or younger
(also, take it all with a grain of salt - little of it is scientifically based, and it's largely just guesswork)