Which element is responsible for spacing between elements

When we need to create some space between two elements that have position: relative and display: block - a common way is to use margin (or padding).

In a vertical context, a common situation is label and input:

<div>
  <label>First name</label>
  <div class='input-wrapper'>
    <input />
  </div>
</div>

Let's say we need 15px of vertical spacing - is there any convention which element should be responsible for the spacing here - ther upper element (label) or the wrapping input div?

The same question could probably be asked for horizontally positioned elements that need space between them.

I know that asking for conventions probably is against the rules at SO, but I'd really like to adhere to a pattern if there is any "industry standard".