Why the new prince could be a rule-breaker: Psychologist Linda Blair explains what your birth order says about you
Are you first-born, middle child or the baby of the family? Clinical psychologist Linda Blair explains what your birth order says about you
The arrival of Prince William and Kate Middleton's third child - a baby boy - is delightful news, but three children means a much richer and more complex set of interactions in a family.
Of course birth order alone doesn't define character - many other factors work together to create a unique individual. However, it is still one of the most powerful factors that shapes character and could be the most powerful influence of all in determining social behaviour throughout our lifetime.
Our siblings - the people we're likely to know for longer than anyone else - are introduced into our lives during our early years, the time when the human brain is developing most rapidly. As a result, our interactions with them create powerful templates that will determine the ways we'll think, feel and behave for the rest of our lives, especially when we're in small social groups.
In 2013, Daniel Eckstein and his colleagues at Sam Houston State University looked at over 200 studies that analysed birth order characteristics and were able to create a list of the most frequently cited qualities for each birth order position.
Based on these findings, it's fairly safe to conclude - bearing in mind no set of qualities can apply to everyone equally - that there are certain characteristics we can expect of an individual depending on their birth order. So what lies in store for all the Cambridge clan?
The eldest is the only child in a family who starts life enjoying the exclusive attention of their parents. As a result, they have more opportunities to develop good linguistic and social skills which means they're likely to do well academically. We can see those good linguistic and social skills in Prince George already.
The downside of all this exclusive attention is that when the next sibling comes along, they feel the loss more keenly than later-borns. This leaves them with a strong thirst for approval from parents and authority figures, and with that comes a powerful drive to succeed.
One study found that first-borns are 30pc more likely to be in positions of leadership than individuals in any other birth order position. First-borns also tend to be more anxious than later-borns. The birth of the first child is an overwhelmingly wonderful experience for parents, but also an anxious time as they come to grips with what being a parent involves. Babies pick up on parental mood, hence the slightly higher anxiety levels that are often characteristic of first-borns.
The arrival of the new baby has meant Princess Charlotte has now become a middle child. Contrary to popular belief, middle children are not brooding and troubled outsiders, but picking up on the more relaxed, confident mood of their (now more experienced) parents, they are often the least anxious child in the family.
They also grow up learning to avoid conflicts and get on with a wide variety of individuals. A word of warning, however: because middle-borns value getting along with others so highly, they can sometimes be easily led and find themselves in trouble.
They're also the children most likely to go through a phase of appearing outlandish in dress or make-up. This may well be their way of reacting to being the child most likely to be overlooked, neither a high-achieving eldest nor adorable youngest.
Youngest of three
To an outsider, this looks like the most privileged birth order position - the new royal baby boy is a lucky child. Like many parents of three, Prince William and Kate Middleton are by now very experienced and more relaxed.
Parents of three have less time to enforce the rules they do set, which allows the youngest child more freedom, both to take greater risks than their older brothers and sisters and to explore more creative domains.
Older members of the family are also often on hand to help, but although this is well intended, it may mean the youngest child grows up feeling impatient and frustrated as they are surrounded by others who are more competent than they are, owing only to greater maturity.
In all of this, it's important to remember there are a number of nuancing factors that can subtly change a child's profile. Age gap is one such factor.
A gap of more than five years means the older child has had a chance to settle into patterns of behaviour typical of a last-born or an only child and that, in turn, means they'll have qualities typical of more than one birth order position.
Similarly, different genders in a family will confound the 'typical' birth positions.
These subtleties are beautifully illustrated in William and Kate's growing family. Because the new baby is a boy, Prince George is now the first-born in two ways, in his ordinal position and as the elder son, so first-born qualities are likely to be strong in him.
Princess Charlotte has a most interesting and complex 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 first-born too.
With a mother who appears empathetic and responsive to needs of others, Charlotte is likely in particular to develop the caring aspects of a first-born and will benefit from the social ease of being a middle child too.
Her younger brother will enjoy many advantages. He has experienced parents and two older siblings to help him grow and develop and he's likely to benefit in wonderful ways.
Linda Blair is a clinical psychologist and author of Siblings: How To Handle Rivalry And Create Lifelong Loving Bonds.