How is the inheritance to be divided among a full brother, four sons of a full brother, two sons of a paternal uncle, and a full sister, given that there is a will stating that all the deceased's possessions should go to two of his nephews, knowing that their father was alive then died before the testator?

What we understand from the question is that the deceased bequeathed all his money to his two nephews, and they were not heirs at the time of the will, but then their brother became an heir after his death. If this is the case, then the will is void because it is a will to an heir, based on the statement of Ibn Qudamah: "If he bequeathed to him while he was not an heir, and then became an heir at the time of death, it becomes void, because the will is considered at the time of death." Furthermore, a will of all property to a non-heir is not effective beyond one-third unless the heirs consent.

If the deceased had no full brother at the time of his death, then the will is void. Half of the estate goes to his full sister, and the other half is equally divided between his full brother's sons. The paternal cousins receive nothing.

However, if he had a living full brother at the time of his death, then the will to the two nephews is valid only within the limits of one-third. Anything exceeding one-third is not effective unless the heirs consent. The remaining portion, after deducting the one-third, is divided between the full brother and the full sister by ta'sib (residuary heirship), with the male receiving the share of two females, as stated in the Almighty's saying: "And if there are brothers and sisters, then for the male is the share of two females" (Quran 4:176). The rest of the mentioned heirs receive nothing. The inheritance is divided into three shares: two shares for the full brother and one share for the full sister.