In Chinese culture, the relationship between siblings is one of the five relationships. As such, it is taken very seriously.
The difference between an elder and younger sibling in Chinese culture is very important, and this relationship is mirrored in the language, as Chinese has different words for the elder and younger brothers and sisters.
As in many cultures, the Chinese will often refer to somone who is not a biological relative as a sibling. This is not just the case in adoptive or foster siblings, but in the case of fellow students of the same teacher.
the four types of siblings in China are: