All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
After the payment of the debts, the estate should be divided among the eligible heirs (as per the Islamic Sharee'ah). If there are no heirs other than those mentioned in the question, the wife is entitled to one-eighth of the estate as a fixed share because of the presence of the deceased's offspring who are entitled to inherit. Allaah, The Exalted, says (what means): {…But if you leave a child, then for them is an eighth of what you leave...} [Quran 4:12]
The remainder of the estate is to be divided equally between the three sons by Ta‘seeb (by virtue of having a paternal relation with the deceased and not having an allotted share, so they get what is left after the allotted shares are distributed). This is based on the statement of the Prophet that reads: “Give the prescribed shares of inheritance to those who are entitled to them; and whatever remains should be given to the closest male relative of the deceased” [Al-Bukhari and Muslim]
Hence, the estate should be divided into 24 shares; the wife gets her share, i.e. one-eighth (3 shares) and each son gets seven shares.
As for the rest of the mentioned relatives, they are totally excluded due to the presence of the deceased's sons.
It should be noted that the division of the inheritance is a serious and critical matter; it is not adequate to settle for seeking a Fatwa in this concern. Instead, you should refer the case to a Sharee'ah-court for investigation; perhaps other heirs entitled to inherit would be discovered in the process. Moreover, the deceased may have left a will or was obligated to debts or may have had other obligations of which the heirs are not aware. It is well-known that the repayment of debts should be given priority over the heirs’ right in the estate. Therefore, you should not divide the estate without referring the case to a Sharee'ah-court, if any, in order to secure the interests of the living and the dead alike.
Allaah Knows best.