It depends. Child styles will inherit modifications made to parent styles as long as the template is not customized in the child style.
For example if your styles are set up like this:
- Master style
|
|- Child 1
|
|- Child 2
Any modification made to a template in the Master style would work in the Child styles. However if you've set it up like this:
- Master Style
|
- Child style 1
|
- Child style 2
You'd have to edit the template for each style.
|