Birth order

The popular picture

The oldest is responsible and bossy. The middle child is the overlooked peacemaker. The youngest is charming and a little spoiled. The only child is mature and perfectionistic. These portraits are everywhere, from magazine quizzes to dinner-table jokes, and they feel true because most of us can name someone who fits.

The idea is often credited to psychologist Alfred Adler, who in the early twentieth century argued that a child’s place in the family shapes how they try to belong. Murray Bowen later included sibling position among the eight concepts of his family systems theory, drawing on research by psychologist Walter Toman. The Bowen Center describes typical tendencies, such as oldest children leaning toward leadership, and notes that no position is better than another.

What large studies found

Earlier birth-order research was often small or compared children from different families, which mixes birth order with family size and background. In 2015, Julia Rohrer, Boris Egloff and Stefan Schmukle analyzed data from more than 20,000 people in the United States, Great Britain and Germany, comparing siblings within the same families as well as across families. Their results in PNAS were striking:

• No birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness or imagination.
• A small, consistent decline in measured intelligence from firstborns to later-borns, along with slightly higher self-rated intellect among firstborns.

A commentary in the same journal by Rodica Damian and Brent Roberts described the evidence as showing little or no substantive relation between birth order and personality. So the research on birth order personality is not simply mixed; the best recent data point toward very small or absent effects on broad traits.

Why it still feels true

If birth order barely moves personality on average, why do family stories about it ring so true? Part of the answer is memory: we notice the bossy oldest who fits and forget the ones who do not. Part is that siblings are compared at different ages, so a twelve-year-old seems more responsible than an eight-year-old simply because she is older. And part is real: families often assign different jobs by position.

Where birth order may matter: roles

An oldest child may be handed more caregiving, especially when a parent is ill or overwhelmed, a pattern that can tip into parentification. A 2025 meta-analysis on favoritism found parents tended to favor older siblings when it came to autonomy and control. Those are differences in experience and expectation, not built-in traits. In other words, the useful question is less “what is my birth order?” and more “what role did my family give me?”

An illustrative example

Picture a couple in Royal Oak who both grew up as oldest children. In arguments they each reach for the steering wheel, and a friend jokes that two firstborns were never going to work. In therapy, they discover the overlap is less about rank than about history: both were the responsible ones in families under strain, and neither learned it was safe to let someone else take charge. That is a story about roles, and roles can change.

Bringing it into relationships

Birth order can be a fun conversation starter with a partner or siblings, and it sometimes surfaces old sibling rivalry. Just hold it lightly. Treat Bowen’s sibling position and other family systems ideas as lenses for reflection rather than predictions. If old sibling patterns keep shaping your marriage or family life, family therapy can help you look at the roles underneath.