Use parent psuedo selectors to affect children

General
1

Is it possible to use pseudo selectors of a parent to affect the behavior of its children?

Example:

<div class="parent">
  <div class="child"></div>
</div>

<style>
.parent:hover .child { 
    width: 100%;
}
</style>
2

Yes, you can use relative styles for that.

image