How is the estate of a man who died leaving behind only a wife and a full brother distributed, knowing that he had two brothers and a sister who died before him, and do the children of the deceased brother inherit anything from this estate?

The inheritance is divided if a man dies leaving a wife, a brother, and a nephew. The wife gets one-fourth due to the absence of a direct descendant, as Allah Almighty says: (And for them [wives] is one fourth of what you leave if you have no child). The remaining portion is taken by the brother, based on the saying of the Prophet, peace and blessings be upon him: (Give the prescribed shares to those who are entitled to them; then whatever remains is for the closest male relative.)