.propertydetailbox2 {
 overflow:auto;
  border: 1px black solid;
 
}
.propertydetailtextbox {
    width: 30%;
 float:left;
    border: 1px solid #cccccc;
    border-radius: 8px;
 margin: 0 auto;
 margin-right:1%;
 padding:20px;
 padding-left:50px;
 height: auto;
 text-align:left;
}
.propertydetailagentbox {
 width: 30%;
 height: 100%;
 float:left;
    border: 1px solid #cccccc;
    border-radius: 8px;
 margin: 0 auto;
 margin-left:1%;
 padding:20px;
}<div class ="propertydetailbox2">
 <div class="propertydetailtextbox">1<br>2<br>3<br>4<br> </div>
  
  <div class="propertydetailagentbox">1<br>2</div>
  
  
  
</div>hi i have one container which contains two boxes (child boxes), i want the parent to take the height of the tallest child which is already done using overflow:auto;, then i want the second child (which is short) to be same height as the parent.  i have tried various solutions given here CSS - Expand float child DIV height to parent's height but using relative and absolute stack the child divs on top of each other, and using  margin-bottom: -99999px;  padding-bottom: 99999px; cuts the border of the second child from the bottom, i need responsive solution.
parent div
.propertydetailbox2 {
    overflow:auto;
}
child1
.propertydetailtextbox {
    width: 30%;
    float:left;
    border: 1px solid #cccccc;
    border-radius: 8px;
    margin: 0 auto;
    margin-right:1%;
    padding:20px;
    padding-left:50px;
    height: auto;
    text-align:left;
}
child2
.propertydetailagentbox {
    width: 30%;
    height: 100%;
    float:left;
    border: 1px solid #cccccc;
    border-radius: 8px;
    margin: 0 auto;
    margin-left:1%;
    padding:20px;
}
please see edit of jsfiddle the divs should be side by side but in jsfiddle they are coming on top of each other
 
     
    