OP, why don't you ask your cousin wife if his husband had bitcoins and did they have some missing bitcoin now after his death and did he ever told if where he kept his private keys in case he is no more in the world. Don't force her to tell you the private keys, Only just for the information if they are missing bitcoins ?


Yes, but there were no @ sign in those addresses or did he replaced the --dashes with @ sign 

Yeah, if the OP can provide a few characters it may be helpful in guessing if this was a private key or something else but i really doubt that it is anything related to private Key.