Referring your question to, Dr. Monzer Kahf, Islamic Economist & Financial Expert, he said,

First, please notice that properties of husband and wife are independent from each other in the Islamic system of law. If they are mixed together; that is every thing is in joint names, we always assume that they own every thing on the basis of half/half. When one of them dies, the estate of the deceased should be distributed to his/her heirs.

Suppose the father dies first; after payment of debts and any special bequeath (through a last will and within the limit of one third), it is distributed as follows: 1/8th to wife and 2/3 to the six girls equally between them. The remaining 5/24 goes to the male or males closest to the deceased. If the mother dies, the share of husband is 1/4, the six girls 2/3 and the remaining 1/12 to the closest male(s) of the mother. If there are no close male relatives of either the remainder is distributed back to six girls equally between them.