What the data actually shows
Studies of parents and their adult children — notably the long-running work of Karl Pillemer and Jill Suitor on within-family differences — find that a clear majority of mothers, when interviewed in depth, can identify a child they feel emotionally closest to or would turn to in a crisis. The differences tend to track things like perceived similarity, shared values, and which child the parent feels they get along with most easily, rather than a simple ranking of love.
Children, for their part, are reasonably good at sensing differential treatment, and they often perceive more of it than parents intend or report. Research in this area finds that a substantial share of siblings believe a brother or sister was favored in some respect, even in families parents describe as even-handed.
On effects, the literature is mixed but points in a recognizable direction: when differential treatment is perceived as unfair, it is associated on average with somewhat poorer wellbeing for the disfavored child — and, notably, sometimes for the favored one too — and with more strained sibling relationships. The associations are modest, the research is largely correlational, and many people who grew up sensing a favorite report no lasting harm at all.
Why this feels different from how it actually is
Favoritism feels like a taboo because the cultural ideal is that parents love their children equally and identically. But 'equally' and 'identically' are not the same thing. A parent can be deeply committed to every child and still find one easier to talk to, share more interests with another, or respond differently to a child's temperament — and children register those differences vividly, often more vividly than the parent does.
Memory also sharpens the sense of being the less-favored one. Slights tend to be more memorable than even-handed moments, and a single remembered episode — who got defended, who got the bigger room, who the parent bragged about — can come to stand in for a whole childhood. The felt pattern can be stronger than the actual pattern.
And birth order, age gaps, and circumstance muddy the picture. The child who needed more help, was sick more often, or arrived during a harder year may have drawn more attention for reasons that had nothing to do with preference — but from the inside, more attention can look a lot like being favored, or being a burden, depending on the angle.
Whether differential treatment harms a child seems to depend far less on whether it happens and far more on whether the child experiences it as unfair.
What the research says to do about it
The most consistent thread in this research is that perceived fairness matters more than identical treatment. Parents who openly acknowledge that different children need different things — and explain why one situation was handled differently — tend to be associated with less resentment than those who insist everything is exactly equal, which children often experience as a denial of what they can plainly see.
For adults carrying the sense of having been the less-favored child, the research on sibling relationships suggests the relationship between siblings is not fixed by childhood dynamics. Sibling closeness commonly shifts across the lifespan, and many strained sibling bonds warm in adulthood once the comparison is no longer happening under the same roof.
Naming the perception, rather than litigating whether it was 'true,' tends to be more useful. Because the harm is tied to felt unfairness, conversations that acknowledge how something felt — without requiring a parent to confess to a ranking that may not exist — are generally more productive than trying to establish an objective verdict about who was loved more.
What the research says does not help
Insisting that all children were treated exactly the same usually does not land, because children can see the differences and hear the denial as gaslighting. The evidence points toward acknowledging difference and explaining it, not erasing it.
Keeping a running ledger of fairness — counting gifts, attention, or defenses to prove a case — tends to entrench the grievance rather than resolve it. Because the felt sense of unfairness is the active ingredient, totting up evidence often keeps the wound open without changing how anyone feels.
Assuming a remembered favorite means a child was unloved is also unsupported. Differential treatment is common and does not, on its own, predict poor outcomes; the modest harms in the research are tied specifically to perceived unfairness, not to the mere existence of a closer bond with one child.
Naming how something felt — without requiring a parent to confess to a ranking that may not exist — tends to be more useful than litigating whether it was 'true.'
What this looks like in real life
Equally is not identically
The cultural ideal is that parents love their children equally and identically — but those are not the same thing. A parent can be deeply committed to every child and still find one easier to talk to, share more interests with another, or respond differently to a child's temperament. Children register those differences vividly, often more vividly than the parent does.
More attention, for reasons that weren't preference
The child who needed more help, was sick more often, or arrived during a harder year may have drawn more attention for reasons that had nothing to do with favoritism. From the inside, though, more attention can look a lot like being favored — or like being a burden — depending on the angle. A single remembered slight can come to stand in for a whole childhood, making the felt pattern stronger than the actual one.
Real numbers in context
Reliable hard numbers are scarce here because so much depends on how favoritism is defined and measured, and most findings come from in-depth interviews rather than large national surveys. In the research on mothers and their adult children, a clear majority can name a child they feel emotionally closest to — but 'closest to' is not the same as loving more, and the share saying they would treat children differently in practical matters is much smaller.
Treat any precise percentage with caution. The honest summary the studies support is directional, not numerical: some differential treatment is the norm rather than the exception, children perceive more of it than parents intend, and the wellbeing effects are real but modest and concentrated where the treatment feels unfair.