This paper describes the inverse marking systems of two closely related Khroskyabs varieties, Siyuewu and Wobzi, and hypothesizes the historical development of the Khroskyabs inverse marking system. I propose that a hypothetical prefix, *Cə-, which is probably related to the second person markers attested in many Trans-Himalayan languages, existed in Proto-Khroskyabs, and that it has different reflexes in the two modern Khroskyabs varieties.