01 February 2026

Siblings, Conflict, and Personalities

This is a question and answer from Facebook (I won't identify the person asking the question, and if you are anyone other than the person asking the question and know what I am referencing, please don't identify them or link to the conversation in the comments). I have added paragraph breaks that the Facebook user interface makes more difficult and less natural to do, for easier reading.

Question

I was raised as an only child. Half and step sibs came later in life, but from birth til leaving home, it was just me. I have felt lucky about this. 

Almost everyone I know with brothers and sisters have had fraught, difficult relationships with them. Is this as common as it seems to me? If you have siblings, has it been an easy relationship or not so much?

My Answer:

Being an only definitely influences your personality, not always for the better (stereotypically, more selfish, better at interacting with adults but less good at interacting with peers, less likely to understand give and take in relationships). 

My relationship with my brother (who is three years younger) is fine, but not super close. Siblings who are one or two years apart tend to have more intense relationships, sometimes for better, and sometimes for worse. Twins, of course, are their own thing (and are almost always on pretty good terms with each other). Big age difference siblings start to be more similar to only children as the age gap gets greater. My two children, who are two years apart, and my wife and her sister, who were two years apart, are probably closer than my brother and I were at three years apart. 

Birth order (oldest, youngest, middle, etc.) also significantly impacts your personality and outlook on lots of thing - it even significantly predicts the side that a scientist is likely to take between two competing scientific theories. 

Both of my children benefitted in their relationships in life from having an opposite sex sibling. People who don't have an opposite sex sibling tend to be more wary of the opposite sex in early puberty. 

As an estate planner and probate lawyer for three decades (I no longer do that work), each additional sibling increases the likelihood of will contests and disputes (even in non-blended families). Families with two full siblings are usually low conflict when the last parent dies. At four full siblings it is 50-50 between high conflict and low conflict. At five or six, there are usually two or three factions among full blooded siblings, at seven or more there are almost always factions. 

Families that have half-siblings and step siblings have much more conflict than families with full siblings, although timing matters a lot. Non-full blood siblings who were pre-teens together living in the same household (or if some were pre-teens and the oldest was a young teen) interact much more like full siblings with each other and also almost never have romantic feelings for each other, unlike those who were never in the same household or started living together as teens or later who are more like roommates with each other and sometimes do have romantic feelings for each other. So sometimes in a blended family, some of the non-full blooded siblings act like full siblings to each other, while others do not.

Post-Script

On balance I think our society as a whole probably loses something of value by having more only children, and by having far fewer middle children, than it did historically, in terms of adult social interactions and in terms of having less variety in personality types when a mix of birth order related personality types is valuable.

Also, while outside my realm of personal experience, it is pretty clear that children raised in polygamous families (usually with many children with each of the sister wives), that at least in Mormon history, those children had less desirable life outcomes than children raised in large monogamous families (with a far small total number of children in the household from their shared father).

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