The arrival of the Duke and Duchess of Cambridge's third child is delightful news - and three children means a much richer and more complex set of interactions in a family.

Many factors work to create a unique individual, but birth order is still one of the most powerful factors that shapes character - and could be the strongest influence in determining social behaviour throughout a lifetime. In 2013, Daniel Eckstein and his colleagues at Sam Houston State University looked at more than 200 studies into birth order characteristics and created a list of the most frequently cited qualities for each birth order position.

Firstborns

The eldest is the only child in a family who starts life enjoying the exclusive attention of their parents. As a result, they often develop good linguistic and social skills and we see these in Prince George already. The downside is that firstborns can pick up on any anxiety new parents may feel and, when the next sibling comes along, they feel the loss more keenly. This leaves them with a strong thirst for approval from authority, and with that comes a powerful drive to succeed. One study found that firstborns were 30 per cent more likely to be in positions of leadership than any other birth order position. Prince George is firstborn in ordinal position and the elder son, so firstborn qualities are likely to be strong in him.

Middle children

Contrary to popular belief, middle children are not troubled outsiders but often the least anxious child in the family. They grow up learning to avoid conflict and get on with a wide variety of individuals. A word of warning: because middle-borns value getting along with others, they can be easily led. They're also the ones most likely to go through a phase of appearing outlandish in dress or makeup - possibly as a reaction to feeling "invisible". Princess Charlotte has a most interesting profile: not only is she now a middle child, but as the first and only girl she is also likely to show characteristics of a firstborn too - particularly caring aspects.

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Britain's Prince William and Kate, Duchess of Cambridge smile as they hold their newborn baby son as they leave the Lindo wing at St Mary's Hospital in London. Photo / AP
Britain's Prince William and Kate, Duchess of Cambridge smile as they hold their newborn baby son as they leave the Lindo wing at St Mary's Hospital in London. Photo / AP

Youngest of three

To an outsider, this looks like the most privileged birth order position - the new royal baby is a lucky child. Parents of three have less time and inclination to enforce the rules, which allows the youngest child more freedom to take greater risks. Older members of the family are often on hand to help, but this can mean the youngest grows up impatient and frustrated as they are surrounded by others more competent than they are. In all this, it's important to remember there are nuancing factors that can subtly change a child's profile and these will be beautifully illustrated in William and Kate's family.