Edit in JSFiddle

<div class="container">
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
</div>
.container { display: flex }

.item {
  padding: 50px;
  background-image: url('https://picsum.photos/id/237/100/100');
}

.container:hover > .item:not(:hover) { filter: blur(3px) }