One of my parents and one of my sibs visualize words for spelling as well. Actually, both of them can visualize books. Ask what happened (or even for a quote) at some point in a familiar or recently-read book , and if they can't name it off the top of their heads, they mentally "look" at the page and re-read it. Which is why they both dislike new editions of old classics!

And yes, both of them have good visual spatial skills.