Янковиц,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
$(".parent").each(function(i, parent) {
$("input.onoffswitch-checkbox", parent).change(function() {
$(parent).parent().nextUntil("li:has(.parent)").filter(":has(.children)").toggle(this.checked)
}).change()
})
});
</script>
</head>
<body> <ul>
<li id="customize-control-12" class="customize-control">
<div class="parent">
<div class="onoffswitch">
<input type="checkbox" id="switch" name="switch" class="onoffswitch-checkbox" value="">
<label class="onoffswitch-label" for="switch"></label>
</div>
<span class="customize-control-title onoffswitch_label">Родитель</span>
</div>
</li>
<li id="customize-control-2" class="customize-control">
<div class="children">
Дочка (должен скрываться)
</div>
</li>
<li id="customize-control-445" class="customize-control">
<div class="children">
Дочка (должен скрываться)
</div>
</li>
<li id="customize-control-23" class="customize-control">
<div class="some-class">
Не должен скрываться
</div>
</li>
<li id="customize-control-435" class="customize-control">
<div class="checkbox_switch parent">
<div class="onoffswitch">
<input type="checkbox" id="switch" name="switch" class="onoffswitch-checkbox" value="">
<label class="onoffswitch-label" for="switch"></label>
</div>
<span class="customize-control-title onoffswitch_label">Родитель</span>
</div>
</li>
<li id="customize-control-426" class="customize-control">
<div class="children">
Дочка (должен скрываться)
</div>
</li>
</ul>
</body>
</html>