I'm sorry to say, but the answer is an absolute NO. With every short sale, all parties are requried to sign an "Arms Length Affidavit" whereby all parties attest that none have any relation to the home owner, among other requirements for completing the short sale. Even the realtors will have to sign this affidavit.
If you are related to homeowner you will NOT be allowed to purchase the home even if he is deceased.
The reason for this is exactly what you stated. You cant afford the house but would want to buy it at an amount that does not satisfy your father's debt to the mortgage company - an unfair advantage that would short change the mortgage holder. Instead, the mortgage company, in an attempt to recover the full debt, only wants the property sold to a buyer who brings the highest and best (certainly fair market) value. There is no sentimental consideration in a short sale as far as the mortgage holder is concerned.