Are you the eldest child in your family? Then your parents have a secret for you
Researchers have found that 74% of mothers and 70% of fathers admit to having a favourite child - and children say there is a bias towards the eldest one.
Sociologists from the University of California performed a study which found the first-born appears to get preferential treatment, and that most parents have a favourite child.
While the parents did not reveal which child was their favourite, the study found that youngest and middle children thought there was a clear bias towards the eldest child.
This knocked their self-esteem.
The study, published in the Journal of Family Psychology, asked pairs of teenage siblings no more than four years apart how they felt their parents treated them.
The researchers found actions as simple as being the first to complete a child made the eldest feel confident and assertive.
Professor Katherine Conger, who lead the study, said before it was completed, they thought older children would feel hard-done-by compared to their siblings - especially as there is a common myth that the youngest child is the favourite and gets the most attention.
They found the opposite - the study of 384 families found the eldest child actually felt their accomplishments meant more to their parents, and this may have been because they were experiencing exam or sporting success with a child for the first time.
Professor Conger said: "I was a little surprised. Our hypothesis was that older, earlier-born children would be more affected by perceptions of differential treatment due to their status as the older child in the family."
The study was in the form of a sociological survey, which asked siblings if they felt differential treatment and whether this has affected their confidence.
Younger siblings said their self-esteem was knocked due to the elder siblings having what was perceived as preferential treatment.