It actually doesn't matter if you're the eldest or the youngest because according to  a latest study, your order of birth in the family has nothing to do with personality development.

A recent massive research which involved 377,000 high school students was conducted to see how much birth order affects their personality development and intelligence. While first borns were found to be slightly more intelligent than younger siblings, the difference was only one point to conclude that while statistically, the difference matters, practically, however, that difference was virtually meaningless.

"In terms of personality traits and how you rate them, a 0.02 correlation doesn't get you anything of note," Brent Roberts, the research's principal author and a psychology professor at the University of Illinois, said in a statement.

The study's co-author Rodica Damian also mentioned that their study sends a clear message to parents that their kids' order of birth should never influence their parenting style "because it's not meaningfully related to your kid's personality or IQ."

This is so far the biggest study that linked birth order and IQ. Also the study employed a rather novel methodology. The siblings were not compared to each other, but rather, the participants were compared with the rest of the sample group. Also, the researchers limited the number of factors into: family size, parental socioeconomic status, family structure, age and gender.

"(Within-family) studies often don't measure the personality of each child individually," Damian explained.

"They just ask one child, usually the oldest, 'Are you more conscientious than your siblings?' "

It was actually Alfred W. Adler, Sigmund Freud's contemporary, who pioneered the idea that birth is determinant of an individual's personality when he grows old. In fact, the researchers noted that it was Adler's ideas about birth order that led to a heated argument with Freud and ended with his resignation from the Psychoanalytic Society. He later founded a new branch of psychology called individual psychology. Adler's idea eventually persisted through the years, despite evidences that contradicted it. Roberts and Damian hope that their study would shed light to this decades-old misconception.