The estate of the deceased who left behind a wife, sons, sisters and grandchildren
Question

                My father passed away recently (may Allah (swt) forgive his sins and bless him) leaving behind family as follows:  
Wife , 4 sons (3 married, 3 grandchildren) ,  3 sisters (one married, one widow, one spinster) ,  Mother and Father .
 I have read the Qur'an, but found the conditions of inheritance a little complicated to understand.
 Please inform me of the correct split of the estate of my father, and also how much, if any, of that estate can go towards charity.
Praise be to Allah.What 
          you have to do is refer to the nearest sharee’ah court to divide the 
          inheritance, after paying any debts that are owed and executing the 
          will of the deceased with regard to one-third or less of the estate. 
          Then the division of the estate among the heirs should be done after 
          the necessary conditions have been met and there is nothing to prevent 
          it being done. In any case, once the necessary conditions have been 
          met and there is nothing to prevent the estate being divided, and there 
          are no other heirs apart from these: 
-The 
          wife should take one-eighth (1/8), because there are offspring who are 
          entitled to inherit. 
-The father 
          should take one-sixth (1/6), because there are male offspring who are 
          entitled to inherit. 
-The mother 
          should take one sixth (1/6) because there are offspring who are entitled 
          to inherit 
-The remaining 
          children should take equal shares, so long as they are all male. But 
          the grandchildren and sisters doe not receive any share, because there 
          are offspring who are entitled to inherit, and these are the sons.