The favourite child is the lucky one. In Emma Robinson’s novel, The Favourite Child, a mother has to choose between twins during a crisis. It is not always that difficult. Research shows that around two-thirds of parents have a favourite child. The questions had to be oblique, because decent parents would never articulate their preference among their children. One study found that favouritism depends on factors such as gender, order of birth, sometimes on conscientious and agreeable personalities, and often on the agreement of values in adult children. Literature shows that the weak or sickly child is often the mother’s favourite. Research indicates that the child who feels neglected or less favoured will remember incidents from his or her childhood and continue to hurt. Such adults have poor mental health, less successful family relationships, and poorer academic achievements. At the same time, it seems that preference may not depend on obvious factors. Neither career accomplishments nor problems such as addiction or getting arrested may affect the mother’s favouritism.

In the ultimate diagnosis, there may be common tendencies that can be listed as part of research, but preference does not necessarily depend on reason. Over-indulgence may spoil the child and turn him or her into a selfish adult with other faults as well. An excellent example of this in the classics is Duryodhana in the Mahabharata. His father’s blind love for him led him to the worst excesses and, finally, to disaster in spite of his mother’s fears. Shakespeare’s King Lear is a more complicated case. The king thought he had been betrayed by his favourite daughter, Cordelia, and transferred his preference to his other two daughters. He bestowed on them all he had, bringing about terrible tragedy for himself and Cordelia. The results can be mixed. Both Achilles’ obstinacy in remaining unmoved by entreaties to fight in the midst of a war and his bodily invulnerability — except in his heel — in the Iliad can be traced back to his mother’s excessive love for him. A mother’s overwhelming love can be fully destructive too. D.H. Lawrence’s Sons and Lovers depicts how a son’s life is blighted because of his mother’s possessive love.

Not that all favourites of parents turn out badly. Elizabeth Bennet in Jane Austen’s Pride and Prejudice, for example, or Jo March in Louisa M. Alcott’s Little Women — the author’s favourite — are both heroines. As for authors’ favourites, Charles Dickens declared, treating all his works as his offspring, that among them David Copperfield was his favourite. In literature, sibling rivalry is a common issue. The Bible provides a telling example in the story of Joseph, whose father prefers him above all his brothers and gives him a many-coloured coat. His jealous brothers try to murder him. But a dangerous story of what favouritism can do is that of Cain and Abel. Perhaps research should also explore to what lengths sibling hatred can go in non-Biblical times.