How is the inheritance divided among two sons and a daughter, and a grandson and a granddaughter (from a son)?

If the deceased has no heirs other than those mentioned, then only his direct sons and daughter inherit, because the sons of the sons are completely excluded from inheritance. The estate is divided into five shares: two shares for the male and one share for the female, in accordance with the verse: "Allah instructs you concerning your children: for the male, what is equal to the share of two females." It is recommended for the children to give a portion of the inheritance to the sons of the sons, in accordance with the verse: "And when [other] relatives and orphans and the needy are present at the time of division, then provide them [something] from it and speak to them words of kindness." It is obligatory to refer inheritance matters to the Sharia (definition) courts for investigation regarding the existence of heirs, wills, or debts that the heirs may not be aware of.