title: One flex/grid item sets the size limit for siblings
body: <p>I have two sibling elements which each contain dynamic content.</p>
  
  <pre><code>&lt;div class="flex"&gt;
      &lt;div class="sibling-1"&gt;&lt;/div&gt;
      &lt;div class="sibling-2"&gt;&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>In some cases <code>sibling-1</code> will have more content then <code>sibling-2</code> and vice versa.
  I would like the height of the second element <code>sibling-2</code> always equal the height of the first <code>sibling-1</code>. If the height of <code>sibling-2</code> is greater then the height of <code>sibling-1</code> it will overflow the <code>flex</code> div and thus be scrollable.</p>
  
  <p>Is there any way to accomplish this with Flexbox? </p>