My father passed away in 1998, and there are five of us kids. My oldest sister was made executor of his estate and out of five kids I am the only known mileage fanatic. My father had 43,000 miles with TWA, so I called them and asked if the miles could be transferred to my account.
The rep said as long as my sister sent a letter stating that she wanted his miles to go to me, and also enclose a copy of his death certificate, than they would be more than willing to do it. And they did.