All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If the deceased had no eligible heirs entitled to inherit other than one son and two daughters, the estate shall be divided between the son and the two daughters by Ta‘seeb (by virtue of having a paternal relation with the deceased without having an allotted share). The male gets twice the share of the female, as Allah Says (what means): {Allah instructs you concerning your children [i.e. their portions of inheritance]: for the male, what is equal to the share of two females...} [Quran 4:11]
Therefore, his estate should be divided into four shares; the son gets two shares, and each daughter gets one share. If any of them passes away before receiving his or her share(s), his right to such shares is not waived by death and is transferred to his or her own heirs, to be divided among them according to the Sharee‘ah inheritance laws. So if the son dies before receiving his share in the estate, it shall be divided among his own eligible heirs. Similarly, if any of the two daughters dies before receiving her share, it shall be divided among her own eligible heirs.
Finally, we would like to draw your attention to the fact that the division of inheritance is a serious and delicate matter. According to the rules of inheritance, there are 15 (categories of) male heirs and 10 (categories of) female heirs who are generally entitled to inherit; the estate cannot be divided except after identifying all the eligible heirs clearly, leaving absolutely no room for ambiguity. Therefore, it is more prudent to not settle for the answer we gave you and refer the case to a Sharee‘ah court or consult a scholar orally for further investigation. There may be other heirs who might not be discovered without careful investigation. Moreover, the deceased may have made bequests or been liable to debts or other obligations and liabilities that the heirs are unaware of. It is well known that the settlement of debts and liabilities is given precedence to the heirs' rights to their shares of the estate. Therefore, you should not divide the estate without referring the case to a Sharee‘ah court, if available, in order to secure the interests of both the living and the dead.
Allah Knows best.