How is the estate distributed for a man who died and left behind a wife, two daughters, a single sister who has two daughters and a son, and he also has deceased nephews and nieces (sons and daughters of brothers and sisters)?

If the heirs of the deceased man are: his wife, his two daughters, and his sister, then his estate is distributed as follows:

The wife: She receives one-eighth (1/8) as a prescribed share due to the presence of the two daughters, based on the Almighty's saying: {But if you have children, then for them is one eighth of what you leave}. The two daughters: They receive two-thirds (2/3) as a prescribed share due to their plurality and the absence of a male counterpart ( عصّب), based on the Almighty's saying: {But if there are [only] daughters, two or more, for them is two thirds of what he left}. The sister: She receives the remainder by way of residuary inheritance (تعصيبًا) due to the presence of the daughters, if she is a full sister or a paternal sister. However, if she is a maternal sister, she receives nothing in the presence of a lineal descendant heir. In that case, the remainder goes to the nearest male residuary heir, based on the Prophet's (peace be upon him) saying: "Give the prescribed shares to their rightful recipients, and whatever remains is for the closest male."

As for anyone who died before the deceased, they do not inherit, because one of the conditions for inheritance is that the heir be alive after the deceased.

It must be noted that matters of inheritance are serious and complex, and a mere fatwa is not sufficient. Rather, it must be referred to the Sharia courts to verify all heirs, wills, and debts, as these take precedence over the rights of the heirs.