The Fasu language of New Guinea is not closely related to other languages, but forms a possible branch of the Trans–New Guinea (TNG) family. Wurm and Hattori (1981) considered its three principal dialects, Fasu, Some, and Namumi, to be three languages, which they called the West Kutubuan family, but Ethnologue

Ethnologue

Ethnologue: Languages of the World is a web and print publication of SIL International , a Christian linguistic service organization, which studies lesser-known languages, to provide the speakers with Bibles in their native language and support their efforts in language development.The Ethnologue...

(2009) considers it a single language. It is not close to the two East Kutubuan languages

East Kutubuan languages

The East Kutubuan languages are a small family of Trans–New Guinea languages in the classification of Malcolm Ross. There are just two languages,which are not close to the West Kutubuan languages. They were linked in a "Kutubuan" family by Franklin and Voorhoeve in 1973, but that position has...

.

Although Fasu has proto-TNG vocabulary, Malcolm Ross

Malcolm Ross

Malcolm David Ross is a linguist and professor at the Australian National University. He has published work on Austronesian and Papuan languages, historical linguistics, and language contact.-External links:**...

considers its traditional inclusion in TNG to be somewhat questionable.