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Every family has the joke. One sibling says, “Well, you were always Mum’s favorite,” and everyone laughs. Parents usually protest that they love all their children equally.
They may well love them equally. But research suggests many parents don’t treat them equally, and the differences follow some surprisingly consistent patterns.
Pooling decades of research
In a study published in 2025 in Psychological Bulletin, Alexander Jensen of Brigham Young University and his colleague McKell Jorgensen-Wells set out to answer a question most siblings have asked at some point: who’s the favorite, and why?
Rather than run a single new study, they combined the results of many. Their meta-analysis drew on 30 published studies and dissertations plus 14 other datasets, together representing 19,469 participants, mostly from the United States and Western Europe.
The researchers looked at favoritism in five ways: overall treatment, positive interactions, negative interactions such as conflict, how resources like money were shared, and how much control or freedom parents gave each child.
Parents leaned towards daughters
Going in, the team expected mothers to favor daughters and fathers to favor sons. Instead, they found that both mothers and fathers were more likely to favor daughters.
The study didn’t explain why. One possibility is that daughters, on average, may have smoother relationships with parents during childhood and adolescence. But the researchers stressed that the findings show patterns, not causes.
Responsible kids got the better deal
Personality mattered too. Children who were conscientious, meaning responsible, organized and self-disciplined, and children who were agreeable, meaning kind and easy to get along with, tended to receive more favorable treatment.
For conscientious children, much of the effect came from conflict. They had fewer clashes with their parents. Jensen suggested parents may simply find these children easier to manage and respond to them more positively.
Jensen said he was surprised that extraversion didn’t make a difference. Outgoing, attention-grabbing children weren’t more likely to be favored. As he put it, being easy or hard to deal with may matter more within families than being the life of the party.
Birth order played a smaller role
Birth order had some effects, though they depended on what kind of favoritism was measured. When it came to freedom and control, parents tended to give older siblings more independence, probably because they were more mature.
Other reports from the research suggested younger siblings often received somewhat warmer treatment in some areas. Overall, though, birth order was a weaker factor than personality and gender.
Why easy kids might feel more rewarding
The study didn’t look at brain activity, but neuroscience offers some clues about why parents may respond more warmly to some children. Positive moments with children, such as smiles, cooperation and affection, engage the brain’s reward system, reinforcing those interactions and making parents more likely to seek them out.
Conflict works the other way. Repeated arguments and defiance can activate the body’s stress system, the HPA axis, leaving parents tense and drained. Over time, it’s easy to see how a parent could drift toward the child who brings more calm and fewer battles, often without realizing it.
Small differences, real consequences
It’s important to keep the findings in perspective. The effects were small, and most parents in the studies treated their children fairly similarly. The research is correlational, so it doesn’t prove that being a daughter or being conscientious causes favoritism.
Still, the differences matter. Jensen noted that siblings who receive less favored treatment tend to have poorer mental health and more strained family relationships. He also pointed out that favoritism isn’t good for the favored child either, since it can breed resentment between siblings.
What parents can do
Jensen’s advice is simple. Pay attention to how each child might be experiencing the family, and ask them about it. Spend time with each child doing things you both enjoy, especially the child who seems harder to connect with.
Children who are more challenging often need extra patience and warmth, not less. And the quieter, harder-to-handle child may be the one who most needs to feel they’re just as loved.
