Birth Order Prediction.

I have developed a theory using which I can tell to a fair degree of accuracy whether a person is an eldest or youngest sibling in a family, or if he/she is the only child depending on the gender of the sibling.

For starters, elder brothers with a younger sister are likely to be more frivolous particularly so if the age difference between them is great. Girls, if they only have a younger sister are likely to have the same fate of being more outgoing and frivolous, not so if their younger sibling is a male. The same goes for males who have an elder brother. The effect becomes greater with increasing age difference between the two.
The healthiest is when the age difference between the two siblings is close to 2-3 years and not more.