Here's why:
* Indo-European Languages are a large family of languages spoken across much of Europe, parts of Asia, and the Americas. Examples include English, Spanish, Hindi, and Russian.
* Romance Languages are a branch of the Indo-European family that evolved from Latin. Examples include Spanish, French, Italian, and Portuguese.
* Greek is an ancient Indo-European language, considered a separate branch from Romance.
* Sino-Tibetan Languages are a completely separate language family, originating in East Asia. Examples include Mandarin Chinese, Tibetan, and Burmese.
Therefore, Sino-Tibetan is the only language family in the list that is not part of the Indo-European family.