Sibling rivalry starts early, as soon as the second child is born. The first child, who till now was the center of everybody’s love and attention feels dethroned. Things can get worse when the third child is born because, so the parents figure, by this time the other two kids are grown enough to take care of themselves.
So the youngest child ends up being pampered while the oldest feels neglected, resulting in a sibling rivalry. The more the age gap between the siblings the more estranged they’re likely to be in adulthood. A different birth order not only contributes to the development of sibling rivalry but also shapes the behavior of siblings when they become adults.
While sibling rivalry may manifest in children as fights over having the best toy or the best chair, it can rear its ugly head in adulthood in property and inheritance disputes. Remember, the competition is for resources and resources facilitate reproductive success. So ultimately, the competition is for reproductive success.
Having an estranged relationship with one’s siblings is distressing because people are wired to rectify relationships with their nearest kin. You may choose to abandon a friend or a lover after having a fight with them but it’s hard to break ties with a sibling who shares half of your genes. Blood is thicker than water.
Role of parents
Parental action can either weaken or strengthen sibling rivalry. If parents blatantly favor one kid over the other, the feelings of resentment in the unfavored kid will deepen. As researcher Judy Dunny puts it, “The greater the difference in the maternal affection and attention, the more the hostility and conflict between the siblings.”
Conversely, parents who don’t practice favoritism and treat all their kids equally and fairly are more likely to raise children less prone to sibling rivalry.