#child2 {
  float: left;
  margin: 0 -120px 0 150px;
}

#child2 {
  order: -1;
  margin: 0 -120px 0 150px;
}

<div id="child2"></div>
<div id="child1"></div>

#parent>div:first-child+div

#parent>div:first-child+div {
margin-right: 20px;
margin-left: 80px;
}

#child2:hover+div {
background: brown;
}

#parent > div:first-child:nth-last-child(2) {
    margin-left:60px;
    margin-right:20px;
}