JSFiddle - React, Tailwind, and code Playground

HTML

<div class="grid-wrapper">
    <div class="box a">A<br>hover</div>
    <div class="box b">B<br>hover</div>
    <div class="box c">C<br>hover</div>
    <div class="box d">D</div>
    <div class="box e">E</div>
    <div class="box f">F</div>
    <div class="box g">G</div>
    <div class="box h">H<br>hover</div>
</div>

CSS

.grid-wrapper {
    display: inline-grid;
    grid-template-columns: repeat(3, 75px);
    grid-template-rows: repeat(3, 75px);
    grid-auto-rows: 75px;
    grid-auto-columns: 75px;
    grid-gap: 10px;
    padding: 10px;
    border: 1px solid black;
}

.a {
  grid-row: 1 / 2;
  grid-column: 1 / 2;
}

.a:hover {
  grid-column: 1 / 4;
  background-color: orange;
}

.b:hover {
  grid-row: 1 / 4;
  grid-column: 1 / 3;
  background-color: aqua;
}

.c:hover ~ .box {
  grid-column: 1 / 4;
  background-color: pink;
}

.h:hover {
  grid-column-end: span 2;
  background-color: green;
}

.box {
  background-color: lightgreen;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
}