Why family members are so different, and how to get along

Siblings: surprisingly different

Parents of more than one child often say their kids were different from day one. Research agrees. Studies of twins and adopted siblings show that personality is partly inherited, often estimated at around 40 to 50 percent of the variation between people. But the part shaped by environment mostly comes from experiences that siblings do not share: different friends, teachers, hobbies, birth order dynamics, and even how parents respond to each child's temperament.

So two siblings growing up in the same home are, in an important sense, growing up in different environments.

The idea of “goodness of fit”

Child development researchers use the phrase goodness of fit to describe how well a child's temperament matches the expectations around them. A highly active child is not a problem in itself, but may be labelled one in a quiet, tightly scheduled household. A cautious child may thrive with a patient parent and struggle with one who pushes for quick independence.

The same idea applies to adults. Many family tensions are less about anyone being difficult and more about a poor fit between personalities and the way the household runs.

Common family friction points

• Planners vs improvisers: one parent schedules every holiday hour, a teenager wants to sleep until noon.
• Talkers vs processors: some family members want to discuss problems immediately, others need time to think first.
• Early birds vs night owls: teenagers naturally drift later; parents often drift earlier. Breakfast becomes a battlefield. See chronotypes explained.
• Different conflict styles: a parent who holds firm and a child who steps back can get stuck in the same argument for years.

Using personality knowledge at home

Describe, don't label

“You need time to think before you answer” is helpful. “You're the difficult one” sticks for life. Personality results should open conversations, not hand out roles.

Adjust the environment, not just the person

If one child concentrates best in the evening, homework after dinner may work better than right after school. If one parent is drained by big gatherings, they can host for part of the day and take a walk in the middle.

Make it a family activity

Quick tests like the chronotype test, travel personality test or conflict style test are fun to take together on a quiet evening. Comparing everyone on one chart often produces laughter and some genuine “so that's why” moments.

A note for parents of teenagers

Adolescence is a period of real personality change: on average, some traits like conscientiousness and agreeableness dip temporarily in early adolescence before rising again into adulthood. If your organised child suddenly isn't, that is normal and usually temporary. Read more in can personality change?.

Adult siblings and ageing parents

Personality differences become important again when adult siblings have to make decisions together, for example about caring for parents. The planner wants a spreadsheet, the empathic sibling wants to talk about feelings, the one who steps back avoids the group chat. Naming these styles openly helps share the load fairly.

Frequently asked questions