Tryit Editor v2.9

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<!DOCTYPE html>
<html>
<head>
<style>
.siblings * { 
    display: block;
    border: 2px solid lightgrey;
    color: lightgrey;
    padding: 5px;
    margin: 15px;
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/jquery.min.js"></script>
<script>
$(document).ready(function(){
    $("h2").nextUntil("h6").css({"color": "red", "border": "2px solid red"});
});
</script>
</head>
<body class="siblings">

<div>div (parent)
  <p>p</p>
  <span>span</span>
  <h2>h2</h2>
  <h3>h3</h3>
  <h4>h4</h4>
  <h5>h5</h5>
  <h6>h6</h6>
  <p>p</p>
</div>

</body>
</html>