Sibling love: Eight facts about a special bond

First-borns are empathetic, last-borns are reckless and "sandwich children" always fall through the cracks. These assumptions about siblings and their birth order are long outdated in sibling research. But one thing is certain: Anyone who grows up with a brother and sister has a lifelong companion - and a lifelong rival.

From my own experience, I know that older sisters think they are smarter for life and younger sisters roll their eyes at them forever. But siblings teach you the subtle nuances between conflict and reconciliation, between rivalry and love. Parents die, marriages fail - siblings stay. Hardly any relationship demands more patience, love and willingness to compromise than that between siblings. After all, this bond is also the longest relationship you will ever have.

Siblings: relationship between love and blows

Let's settle this once and for all: who is really smarter and who is more willing to take risks? And how often do siblings argue per hour to find out? Eight exciting sibling facts to amaze and make you smile.

1. firstborns are smarter

I'd better get the unpleasant news out of the way straight away: many clichés about sibling relationships are outdated and untrue. But when it comes to IQ, there seems to be a consensus among scientists: Older siblings are the smarter ones.

This conclusion was first clearly reached in a study from 2007, which was published in the journal "Nature" and received much scientific popularity in the years that followed. However, according to the researchers, IQ differences between siblings are small and are due to family dynamics - not biology.

Older siblings share their knowledge at an early age and thus take on a kind of "tutoring job" for their younger sister or brother. Another explanation is related to the first: Because older siblings quickly occupy the monopoly on the role of the smarter one, younger siblings develop other skills in order to stand out in the family dynamic: they become particularly creative or acquire particularly strong social skills.

2. siblings want to be different

"Sibling love" is a human construct and is rarely found in the animal world. In the beginning, siblings are one thing above all: rivals. For the TV remote control and for the favour of their parents. Differentiating yourself from your siblings in terms of role and character is therefore evolutionary: From an early age, you carve out a niche for yourself within your family.

The "Sibling Niche Differentiation Model" was first established in 1996 by psychologist Frank Sulloway. He assumed that siblings compete for their parents' resources - and that being different therefore proves to be an evolutionary advantage in the family system. Sulloway's model has since been confirmed in studies: It is not so much your position within the family that shapes your personality, but how strongly you had to differentiate yourself from your siblings.

3. eight times an hour: that's how often siblings argue

This is why your siblings are not only lifelong partners, but also lifelong sources of friction. They are proof of your uniqueness. This is also how Jeanine Vivona, Professor of Psychology at the College of New Jersey, explains sibling rivalry. In one of her studies, she writes: "In the long run, differentiation from siblings serves to mitigate rivalry and conflict among them." You hardly ever learn to be as bluntly honest about your feelings with anyone as you do with your siblings. And that's what makes your relationship so resilient.

This took a lot of conflict in childhood: on average, siblings argue up to eight times an hour. Two sisters are more peaceful with each other than siblings with one brother. If you want to put a positive spin on it: You get to know each other when you argue, and friction ultimately generates warmth.

4. Lastborns are not more willing to take risks

For a long time, it was considered common practice that lastborns are reckless, fearless and risk-takers. This assumption is based not least on Sulloway's niche theory: he noted that political and scientific revolutionaries are often lastborns - for example Charles Darwin or Alexander von Humboldt.

However, a longitudinal study with 30,000 respondents shows that the willingness to take risks is not related to birth order. The head of research at the Max Planck Institute, Ralph Hertwig, says: "The hypothesis that family dynamics, which in turn could be characterised by birth order, influence the willingness to take risks seems quite intuitive and plausible. But we were unable to find any evidence in favour of this theory."

5. Apropos: Your job shapes you more than birth order

Whether you were born first or last in the birth order may have determined who controlled the TV programme in your childhood. However, birth order has far less influence on your development than you might think. In a US study, researchers found no significant influence of the order in which siblings are born on personality. It's a different story with your first job at work: New demands on performance and behaviour at work shape your personality significantly more than the arbitrariness of your family position.

6. siblings influence your well-being

The quality of your sibling relationship is something that shapes you throughout your life. This is shown by various studies, such as in the journal "Family Relations" or in the "Journal of Youth and Adolescence. A warm, supportive relationship with your siblings will help you achieve your goals. In contrast, aggressive and exclusionary behaviour with each other is linked to depression and low self-esteem. And studies on twins show just how positive a warm sibling relationship can be for your life:

7. twins live longer

There were 1258 twin births in Switzerland in 2022. While siblings usually share between 25 and 75 per cent of their genetic material (depending on the proportion they inherit from their mother and father; theoretically, a genetic match of 0 per cent is also possible), the DNA of identical twins is 100 per cent identical.

This makes their connection so special.

This makes their bond particularly strong. A Danish study analysed 2932 pairs of identical twins and came to the astonishing conclusion that identical twins live longer than fraternal twins or the rest of the average population. The researchers cite three reasons:

Twins give each other emotional support in difficult times. Because they are genetically so similar, they know each other particularly well and can respond to his or her needs in an ideal way. And: twins protect each other, avoid risky behaviour and encourage healthy behaviour in each other. And this life-prolonging effect can be achieved by all sibling pairs - it is not exclusively written into the DNA of twins.

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8. Every fifth child is an only child

Not all children in Switzerland have the benefit of a sister or brother. An average woman has 1.5 children here - half as many as during the baby boom in the 1960s. This is why households with individual children are becoming increasingly common in Switzerland: one in five children here is now an only child.

Not necessarily to the detriment of the child: It saves a lot of bickering and endless tussles and is assertive in the end.