JSFiddle - React, Tailwind, and code Playground

HTML

<div id="icon">
<div class="test-1">Кнопка</div>
<div class="parent">
<div class="children-1">первый</div>
<div class="children-2">второй</div>
<div class="children-1">третий</div>
</div>
</div>

JavaScript

$(".test-1").on("click", function() {
  $(this).next().find("div[class$='en-1']:first").css('color','red')
});