The real reason you’re so different from your sibling
Have you ever wondered why you’re the opposite of your brother or sister? Despite living under the same roof with the same parents and sharing about half of the same DNA, research has shown sibling personalities are about as similar to each other as a random stranger! This isn’t random. It’s strategic.
Sibling De-identification
While it may seem natural to identify with your immediate family, siblings tend to do the opposite. Sibling de-identification is a reactive response during identity formation in childhood and adolescence. Rather than focusing on each other’s commonalities, siblings intentionally tend to define themselves based on their differences. This natural, adaptive, and often unconscious process lets siblings be seen for who they are.
Niche Picking
Developmental psychologists call the process of how siblings choose to differentiate niche picking. Rather than compete directly with an identity another sibling is already known for, siblings proactively claim a unique perceptual psychological space in the minds of parents. By carving out distinct ownable roles, achievements, and even personality traits, siblings vie for attention as an adaptive strategy to maximise parental attention and investment.
In other words, if your brother was already seen as the “smart one”, you may have claimed the territory of the “funny one.” If your sister established her role as the “athlete,” you may have fashioned yourself the “artist.” And if your sister or brother was always praised for being the “good girl/boy,” you may have revelled in your role as the “rebel,” “free spirit,” or “changemaker.”
Parental Perception Is Key
This doesn’t mean you’re not smart, athletic, or a nice person. It just means that someone else beat you to the punch, so you felt compelled to choose another path. According to evolutionary psychologists, investing time, resources, and energy is costly for parents, so they often invest in their offspring who promise the best long-term payouts and return on investment. Therefore, when choosing a niche, it is not enough to stand apart; you must also appeal to the opinions of the people that matter most: your parents.
You don’t grow up in the “same house” as your siblings because circumstances change, family dynamics evolve, and parents treat kids differently based on positioning, not just person. External environmental factors like parental expectations, birth order, sibling roles, and family values can heavily influence who you become.
And while niche picking can empower you to be seen, this only happens when you choose a niche that suits you. Choosing the wrong niche can risk unfavourable life outcomes, especially if you don’t choose one that you’re genuinely interested in or naturally good at.
The Damage of Parental Differential Treatment
A recent research study conducted by Jensen and Jorgensen-Wells (2025) analysed a very large data set of over 19,000 participants and confirmed the long-term developmental consequences of parental differential treatment. The article published recently in Psychological Bulletin observes: “Decades of research highlight that differential treatment can have negative developmental consequences, particularly for less favored siblings.”
The researchers found that parents tend to provide favourable treatment to the children perceived to be more agreeable and conscientious. Favourable treatment was associated with better, longer-term outcomes, like better psychological health, fewer behavioural problems, and healthier relationships.
In addition, the research findings suggest that younger siblings and sons may be prone to less favourable treatment, placing these individuals at higher risk for negative developmental outcomes. The authors warn: “Parents and clinicians should be aware of which children in a family tend to be favoured as a way of recognising potentially damaging family patterns.”
Reclaim Your True Self
If this pattern, for whatever reason, feels like your life experiences, it’s never too late to reposition yourself. Identity formation is a process, not a fixed entity. There are vast amounts of research showing that living an authentic life by aligning your sense of self with your values and beliefs is associated with greater psychological well-being and life satisfaction.
Pick a New Niche
Try this again, but this time around, flip the script. Instead of choosing a niche focusing on what others want, focus only on what you want. Try out new activities, hobbies, social engagements, careers, etc., based only on your passions and proclivities (not how you compare to others). What may have started off as an unconscious protective defence can become a conscious reclamation of authentic self-expression and personal growth.