JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
  <li><a href="link">Item 1</a>
    <ul>
      <li><a href="link">Item 1.1</a></li>
      <li><a href="link">Item 1.2</a></li>
      <li><a href="link">Item 1.3</a></li>
    </ul>
  </li>
</ul>

CSS

li:hover {font-weight: bold;}

li:hover li {font-weight: normal;}

li:hover li:hover {font-weight:normal;}