Something that everyone says he/she got least attention, most relational stress, and best personality from. Only child always say that he/she is lonely.
typical stereotyping goes as follows:
first born - bossy but responsible/independant
middle child - ignored but mediator/peace maker
youngest born - spoiled but nice/humorous
only child - jesus
In fact, according to a census done by Julius Caesar in 8th century, the first child suffers the most from lack of attention and the stress from the family. It's also proven that it's the birth order that develops the best personality.