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 is His slave and Messenger.
If the deceased did not leave any other heirs except those mentioned in the question, then his mother gets one-sixth as her legal share due to the existence of two brothers of the deceased, as Allaah Says (what means): {And if he had brothers [and/or sisters], for his mother is a sixth, after any bequest he [may have] made or debt.}[Quran 4:11]
The remainder should be given to the father 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 have been distributed); as the Prophet said: “Give the prescribed share of inheritance to those who are liable for it and the remainder [of it] is for the nearest male blood relative." [Al-Bukhari and Muslim]
However, the brother and the sister do not get anything from the inheritance because they are prevented by the existence of the father.
Therefore, the inheritance should be divided into 6 shares, the mother gets one-sixth, which is 1 share, and the remainder is 5 shares for the father.
Allaah Knows best.