Как вариант...
<!DOCTYPE html>
<html>
<head>
<style type="text/css">
.block2 {
display: none;
}
.block-ONE:hover > .block2 {
display: block;
}
.block-TWO:hover > .block2 {
display: block;
}
</style>
<script type="text/javascript">
</script>
</head>
<body>
<div class="block-ONE">
block-ONE
<div class="block2">block2 ONE</div>
</div>
<div class="block-TWO">
block-TWO
<div class="block2">block2 TWO</div>
</div>
</body>
</html>
И никакого jQuery...