Sounds legit to me; I'm pretty sure standard practice in cases of unclaimed inheritance is to just randomly find someone with the same surname in the phone book and give the money to them. I keep waiting for my windfall but sadly my surname is quite rare
Write back in "amazement" because Mr Hoskins Hughes IS your long lost brother, who moved to Thailand in 1983 and you haven't heard from him since. Hence, you will be claiming the entire $5.5M.........