A man died and left behind two wives, five sons and a daughter, then the first wife and one of her sons died

Firstly: 

If a man died and left behind two wives, five sons and one daughter, and he did not leave behind any heir other than these, i.e., he had no father, no mother and no grandfather, then the two wives inherit one-eighth, which is shared between them. Allaah says (interpretation of the meaning): “but if you leave a child, they get an eighth of that which you leave” [al-Nisa’ 4:12]. 

The rest is to be shared among the children, with the male getting the share of two females; there is no difference between the children of one wife and another. 

In this case, the estate is to be divided into eight shares, of which the two wives get one. The rest — which is seven shares — is to be divided among the children. This may be done by dividing the estate into 176 parts, of which 22 go to the two wives, and the rest to the children. 

So the share of each wife = the estate x (11 / 176) 

The share of the daughter = the estate x (14 / 176) 

The share of each male = the estate x (28 / 176). 

Secondly: 

If the first wife has died, her heirs inherit from her, and they are her two sons, her father, her mother, and her grandmother, if they are alive – and nothing goes to the children of the second wife.  

Then if one of the sons of the first wife dies, his estate goes to his heirs. So we have to see whether he had children and a wife or not. If he did not, then his entire estate goes to his brother. 

If the first wife died along with one of her sons at the same moment, then this son does not inherit from his mother, and their estate goes to their heirs: the estate of the wife goes to her living son and to her father, mother or grandmother if they are alive. 

The entire estate of the son goes to his brother — if he did not have a child or wife — as stated above. 

And Allaah knows best.