JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <div class="sibling">
    </div>
</div>

CSS

.parent{
    position: relative;
    width: 800px;
    height:400px;
    background-color:red;
}
.sibling{
    bottom: 0;
    left: 50%;
    margin-left: -150px;
    position: absolute;
    width:300px;
    height:50px;
    background-color: green;
}