An only child is a child with no siblings, either biological or adopted. Although first-born children may be temporarily considered only children, and have a similar early family environment, the term only child is generally applied only to those individuals who never have siblings. An "only child", however, may have half-siblings or step-siblings who come along considerably late (after they reach their teens) and still be considered an "only child". Children with much older siblings (generally ten or more years) may also have a similar family environment to only children.
Families may have an only child for a variety of reasons, including: personal preference, family planning, financial and emotional or physical health issues, stress in the family, time constraints, fears over pregnancy, advanced age, infertility, divorce, and death of a sibling or parent. Under the one-child policy in Mainland China, subject to local relaxations and individual circumstances, urban parents are generally prohibited by law to have more than one child.
Only children are often subject to a stereotype that equates them with spoiled brats in Western countries. In China, the phenomenon of Little Emperor Syndrome has been observed.
In recent years, the number of families in the United States choosing to have one child has increased considerably. New York City is famous for residents with increasingly popular single-child families, and a 2005 article concluded that more than 40% of the city's residents have an only child. This can be attributed mainly to socioeconomic, educational, career, and financial factors. A similar trend is also prevalent in Europe, where only children are widespread and common. -source: wikipedia.com
Onlies are awesome.