When an only child suddenly gets siblings (step siblings/baby brother or sister) and realizes that the adult attention he or she once enjoyed so much and took for granted suddenly is scarce, resulting in a feeling of sadness and loss.
Peter was used to being the only child, but due to his mother's remarrying, he got new step siblings. Not being used to fight for attention from his mother, he has hit with an only-child-hangover.
by tabu.post April 20, 2011