Removing Permanent Marker Pen

Sorry - I'm afraid I don't. However, I do know a fairly cheap way of getting rid of really dark paint (dark purple - I was obviously having a crisis!). Rather than spending a fortune on all the coats of paint needed to get rid of a dark colour instead I opted for wallpaper as it was only on one wall. I know I know, it's all the fashion and surely becoming really really dull now but actually it looks great and didn't cost that much at all.

Nope, but I know how to get permanent marker of a whiteboard.

Not quite the same thing

It sounds like a good reason to redecorate some of your house! Maybe it could also be used as an educational experience for your nephew - how often has he done that in his own home.

Solvent is the only way to do it and I shouldn't imagine it will do your wallpaper much good

Well, I guess that there is a good reason why it is called 'permanent marker' - it marks permanently.
If it didn't do that, the manufacturers would be liable under the trades description act.