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 wife did not leave any heirs other than those mentioned in the question, then her mother gets one-sixth as her legal share due to the existence of direct heirs (children) and sisters, as Allah Says (what means): {And for one’s parents, to each one of them is a sixth of his estate if he left children.} [Quran 4:11]
Her husband gets one-fourth as his legal share due to the existence of the children (direct heirs); Allah Says (what means): {But if they have a child, for you is one fourth of what they leave, after any bequest they [may have] made or debt.} [Quran 4:12]
Her daughters get two-thirds as their legal share as Allah Says about the existence of a number of daughters (what means): {But if there are [only] daughters, two or more, for them is two thirds of one’s estate.} [Quran 4:11]
However, the two full-brothers do not get anything from the inheritance because they do not have a specific share in the inheritance and they only inherit what remains after the share of the heirs [who have specific shares]. But in this present case, there is nothing left for them from the inheritance.
To sum it up, the inheritance should be divided into 39 shares; the mother of the deceased gets 6 shares; her husband gets 9 shares, and her daughters get 24 shares, each daughter gets 4 shares.
Allah knows best.