<ul class="my-class">
  <li>First</li>
  <li><a>Second</a></li>
  <li class="find-siblings">All of my siblings turned red, <em> but my child</em><strong>ren didn't!</strong></li>
  <li><a><span>Third</span></a></li>
  <li><a><span>Fourth</span></a></li>
</ul>
<ul class="my-class">
  <li><a><span>Fifth</span></a></li>
  <li><a><span>Sixth</span> <em>Sixth</em> <span >Sixth</span></a></li>
  <li class="find-siblings"><a>Seventh</a></li>
  <li><a>Eighth</a></li>
</ul>
html {
  background: #fbdf00;
  font-size: 20px;
}
// selects only the first '.find-siblings' element
let item = document.querySelector('.find-siblings');

// :scope is necessary for preventing the child elements of 'item' from being selected
// see what happens to the text when you remove ':scope >'
let siblings = item.parentNode.querySelectorAll(':scope > :not(.find-siblings)');

// loop through the siblings
for (let i = 0; i < siblings.length; i++) {
    siblings[i].style.color = 'red';
}

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External JavaScript

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