CREATE TABLE table_15994 ("Case/Suffix" TEXT, "we two" TEXT, "you and I" TEXT, "you two" TEXT, "them two  ( the two ) " TEXT, "who-two" TEXT)

What is who-two when you two is ngipelngu?
SELECT "who-two" FROM table_15994 WHERE "you two" = 'ngipelngu'
SELECT "who-two" FROM "table_15994" WHERE "you two" = 'ngipelngu'