What is a distinctive feature of the Indo-European language family?

A distinctive feature of the Indo-European language family is that it is spoken by nearly half of the world's population. This language family includes many widely spoken languages such as English, Spanish, Hindi, and Russian, which are used as first languages and in various international contexts. The prevalence of these languages contributes significantly to the total number of speakers within the Indo-European family, reflecting its global influence.

The other aspects mentioned in the options do not accurately represent the Indo-European language family. For instance, it is not the least spoken family; in fact, it includes some of the most widely spoken languages worldwide. The Indo-European family also has a rich history of written forms, with many languages in the family having extensive literature and records. Additionally, the family is not declining in usage overall; many of its languages are growing in speakers and presence, particularly due to globalization and migration patterns.