Show Parent Menu children in sidebar I want to explain this as simple as possible... 

I have a main navigation placed into the main_navigation block in my site
and I want to add a sidebar menu if the CURRENT main_navigation page has
child menus...

For example:


My main navigation is: Home | About | Services | Blog | Contact
Us 
I added Request Quote page/form as a child of Contact Us 
so when I am in Contact Us page, I want to show Request Quote in the
sidebar but don't show it if I am in About or Services


I saw this question but can't duplicate it 

Get menu link siblings

Any help is welcome!
Use the Menu Block module, create a new Menu Block using the Primary Navigation, starting at Level 2. 

This will only show the children of the current parent menu item you are in.