What is the Sharia ruling or prescribed expiation for a boy under ten who committed sodomy with his brother under eight, and what is the psychological treatment to overcome the recollection of this incident?

The hadd (punishment) for sodomy is not applied to a non-pubescent individual, nor is a specific kaffarah (definition) (expiation) obligatory upon him, because "only an adult is to be stoned." If this person needs to consult a trustworthy psychiatrist, there is no harm in it. However, he should not disclose to the psychiatrist, from what must be concealed of his reprehensible act, anything more than what necessity dictates.