<!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/3.7.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("li.start").prev().css({"color": "red", "border": "2px solid red"});
});
</script>
</head>
<body>
<div style="width:500px;" class="siblings">
<ul>ul (parent)
<li>li (sibling)</li>
<li>li (the previous sibling of li with class name "start")</li>
<li class="start">li (sibling with class name "start")</li>
<li>li (sibling)</li>
<li>li (sibling)</li>
</ul>
</div>
</body>
</html>