body {
  display: flex;
  justify-content: center;
}

.container {
  background-color: yellow;
  display: flex;
  width: 200px;
  height: fit-content;
  margin: 0 10px;
  justify-content: space-around;
}

.container.firstCheck{
  flex-grow: 1;
}
.container.secondCheck{
  flex-grow: 1;
}

<div class="container">
  <div class="checkboxes">
    <div class="firstCheck">
      <label for="check1">this is 1</label>
      <input name="check1" type="checkbox"/>
    </div>
    <div class="SecondCheck">
      <label for="check2">this is 2</label>
      <input name="check2" type="checkbox"/>
    </div>
  </div>
</div>