There has been some debate over whether they are closer to each other than to other languages, but Usher includes them both in the Kikorian branch of the tentative Papuan Gulf stock.
Within the two branches, the lexicostatistical figures are 60–70%. Between the two branches, they are 10–20%.
papa ‘mother’s sister’ < *mbamba ‘older same sex sibling’
ira ‘tree’ < *inda
sakipu ‘sand’ < *sa(ŋg,k)asiŋ
kupa ‘wind’ < *kumbutu
^Pawley, Andrew; Hammarström, Harald (2018). "The Trans New Guinea family". In Palmer, Bill (ed.). The Languages and Linguistics of the New Guinea Area: A Comprehensive Guide. The World of Linguistics. 4. Berlin: De Gruyter Mouton. pp. 21–196. ISBN978-3-11-028642-7.