Being a firstborn has its benefits. A 2007 study published by Norwegian researchers in journals and showed firstborns are generally smarter than younger siblings, enjoying an IQ that is on average three points higher than the next eldest.

This may simply be due to a tendency among parents to lavish resources on their firstborn. A study by Brigham Young University's professor Joseph Price released in 2008 in the found that parents gave their firstborn child about 3,000 more hours of quality time between the ages of four and 13 compared to the next sibling.

As other siblings arrive, however, having to share mum and dad's attention may cause resentment and insecurity. According to Adler, firstborns may feel "dethroned".

Rebecca Simpson is the second of five siblings; now that she has a child of her own, she can understand the friction in her childhood.

"As a parent, I can see why my eldest sister hated me coming along," she says. "Our daughter is lavished with love and attention, like any first child. When we have our second child, it will be a shock for her."

Firstborns also face added pressure as parents often impose more severe discipline on them as a way to deter younger children from behaving badly, according to research published in in 2008.

With first-time parents anxious that everything should be perfect for their child, firstborns are prone to stress, says Cora Ha Chan Wai-Luen of parenting consultancy Family Foundations. And as parents gain confidence in their child-raising skills, they will become more relaxed, and so will a second child who comes along.

Second or middle children are usually more people-oriented. As marketing manager of Bloom & Grow, Simpson has a job that perfectly matches her position in the pecking order, if psychologist Catherine Salmon's research is anything to go by. Writing with journalist Katrin Schumann in , she concludes: "Middles are self-aware team players with remarkable diplomatic skills. Because they're outgoing and flexible, they tend to deal well with others - in the workplace and at home."

Although middle children may feel neglected and overshadowed, the authors believe their people skills can lead them to thriving social lives and flourishing careers.

Even so, successful middle children can suffer low self-esteem "because they are neither top of the food chain nor the most loved baby", Ha says. The conflicted feelings may cause them to rebel or try harder to stand out in the family.

Stay-at-home mum Virginie Zurcher can see the parallels in her family. "My middle brother always sought my parents' attention and love, especially as we felt like our mum had a slight preference towards our eldest brother," says Zurcher, youngest of three siblings. "So my middle brother engaged in entirely different activities, to be acknowledged and avoid comparison. He started hiking and now he has reached some of the highest mountains. He liked motorbikes, and now he has travelled along some of the most difficult roads in the world. His 'middle child syndrome' actually had a very positive effect on his life."

However, with three children aged five, three and six months, Nadine Lecocq is determined to ensure that her middle child, Julien, won't feel overlooked.

Realising that her eldest son Oliver, a typical firstborn, tends to take up more of her attention, Lecocq is making a conscious effort to spend equal time with Julien.

"I am trying hard at the moment to talk to Julien and spend time reading, writing and doing activities with him when Oliver isn't around and Angus is sleeping," she says. "It is hard as this is typically my time to catch up on tasks. But I think back to when Oliver was the same age and want to make sure I give Julien the same attention that I gave to him."

By the time a third child arrives, parents may be too exhausted to bother with the rules and these children tend to be more relaxed and prepared to take risks, Ha says.

"Doted on by their parents and siblings, they are secure in people's love for them and can get away with things because they are cute."

As a last born child, Zurcher concedes she's not the driven type and won't lose too much sleep if she fails to meet her goals. Simpson describes her youngest sibling, now 20, as "the fun-loving, charming baby of the family, who is reliant on his older sisters". Tee says her youngest sibling is "more relaxed, laid-back and lives for the moment".

But expectant mum Shireen Nasser, the youngest of four siblings, says: "By the time I was born, the novelty had worn off for mum and she went back to work full time. Sure, she loves me lots, but anything I do, three others have done before me so my experiences are no big deal."

It is obvious how typical birth order traits may come about; but factors such as the age gap between siblings, their gender, and the number of children also come into play, as do the influence of blended families and other life experiences.

But parents need to be aware of the typical traits, Ha says. Because differential treatment can rouse rivalry, they can make more of an effort to offer balance. Each child needs a different kind of attention.

"Be affirming to firstborns, especially during times of failure," she advises. "Teach them to be gracious to themselves and others. For middleborns, take the time to be a talent scout to ensure their unique gifts are acknowledged and supported. Encourage lastborns to pull their weight and allow room for their personalities to develop."

And while some parents worry about more squabbling in larger families, others such as Lecocq reckon a larger brood can bring more learning opportunities and enrich home life. "Ultimately, I see that we are there to prepare our children for life," she says. "Some of the most important skills are how to develop relationships with others, how to get along with others, how to respect others. Yes, my husband and I were concerned about being outnumbered and having a 'middle child'; but, for us, the relationship argument won in the end."