But where did the the birth-order theory actually come from, and is there any truth to it?
Read on for more on birth-order theory.
Where did birth-order theory come from?

Photo: Claudette Barius/HBO
Whats the birth-order theory conception of an oldest child?
What about a middle child?
(Fun celebrity fact:Bella Hadidis a middle child!)
And a youngest child?
(Amy Marchburning her older sister Jos manuscript inLittle Women?
Why is birth-order theory suddenly everywhere?
Elsewhere, users like@t0nit0nehave broken down the compatibility of different birth-order pairings.
(Hint: Its better to be a firstborn involved with a lastborn than a firstborn with another firstborn.
Youve been warned!)