If the fiancé dies before the marriage contract, does his fiancée inherit from him?
Question

                A man proposed marriage to a woman and her relatives agreed to that, and they agreed on the mahr with him, but he did not pay it. Then the fiancé died. What is the ruling on that? Does the woman in question inherit from him and should she observe mourning for him?.
Praise be to Allah.
      If the situation is as you describe in the question, and 
      the marriage contract had not been done between them, with the proposal 
      from the woman's guardian and acceptance from the husband, whilst 
      fulfilling all the conditions of marriage, with no impediments, then the 
      woman mentioned does not inherit and she does not have to observe ‘iddah 
      or mourning, because she is not a wife to her fiancé; rather she is still 
      a stranger or non-mahram to him, because the marriage contract had not 
      been done; rather all that happened was engagement and agreement with her 
      relatives on the mahr only. This on its own is not regarded as a marriage, 
      and there is no difference of opinion among the scholars (may Allah have 
      mercy on them) concerning that. And if the family of the fiancée had taken 
      any money from him, they have to give it back to his heirs. End quote. 

    Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him)