Like many languages (but unlike Greek or Hebrew or English), Tuvan uses a formal vs. informal 2nd person pronoun (a familiar vs. a respectful “you”). Unlike other languages that have this feature, however, the translators of the Tuvan Bible have attempted to be very consistent in using the different forms of address in every case a 2nd person pronoun has to be used in the translation of the biblical text.
As Voinov shows in Pronominal Theology in Translating the Gospels (in: The Bible Translator 2002, p. 210ff.), the choice to use either of the pronouns many times involved theological judgment. While the formal pronoun can signal personal distance or a social/power distance between the speaker and addressee, the informal pronoun can indicate familiarity or social/power equality between speaker and addressee.
Here, Jesus’ brothers address Jesus with the informal pronoun.
Vitaly Voinov explains: “Whether one believes that these were Jesus’ younger brothers, his older half¬brothers, or his cousins, it seems that their familial intimacy coupled with a lack of faith and respect would preclude them from using a polite form in addressing Jesus. Using the informal address here in the Tuvan text is an excellent means to reinforce their expression of disbelief and possible mockery of Jesus’ mission.”