Oh no the kid went wild with the sharpie pen. ouch.

Sharpie pen on curtain.
We found this and you might find it helpful.
We can give no guarantees that any of it works but try a it on tiny piece of fabric on the hem or the inside of a side fold.
If there is no colour loss then try a bigger spot. If that’s still good then try it on the pen stain.

Kids drawn all over your curtain.