I am just adding up the figures, you want someone aged 55, assuming your grandfather is of that age, your father must be at least 20 years younger, that is, 35, now you must be at least 20 years younger to your father, ie, 15
Its not a child's play to fiddle with adult picture kid
Btw, would like to see a pic of your grandfather to see if there is anyone who is kinda alike and try to convince for a adult selfie.