You don't parent dynamic  clothing props.

Ice-boy, this cape is not the easiest thing to work with, in fact it's probably the most difficult dynamic item that I've run across so far. 

Can I suggest abandoning this cape and finding something   easier  to work with for the time being until you get more experience in Poser and the cloth room?

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi