What is the share of each heir from the inheritance, given that the deceased's heirs are: a wife, two full brothers, and a full brother's son?

The deceased's wife receives one-quarter due to the absence of a direct heir. His two full sisters receive two-thirds. The remainder goes to his full brother's son by virtue of 'asabah (agnatic relationship). The estate is divided into twelve shares: the wife receives three, the two sisters receive eight, and the brother's son receives one.