I have two divs that are not nested, one below the other. They are both within one parent div, and this parent div repeats itself. So essentially:

```
<div id='parent_div_1'>
  <div class='child_div_1'></div>
  <div class='child_div_2'></div>
</div>

<div id='parent_div_2'>
  <div class='child_div_1'></div>
  <div class='child_div_2'></div>
</div>

<div id='parent_div_3'>
  <div class='child_div_1'></div>
  <div class='child_div_2'></div>
</div>

```

I want to get each pair of `child_div_1` and `child_div_2` next to each other. How can I do this?