You can use the has method to get the elements that has children that matches a selector, intead of looping through the children yourself:
$('#combineDiv').children().has('.combinedColumn:first-child').each(function(){
alert('found ONE!');
});
Example:
With this HTML:
<div id ="combineDiv">
<div><span class="none">1</span><span class="none">1</span></div>
<div><span class="none">2</span><span class="combinedColumn">2</span></div>
<div><span class="combinedColumn">3</span><span class="none">3</span></div>
<div><span class="combinedColumn">4</span><span class="combinedColumn">4</span></div>
</div>
This will match the third and fourth child div and make their background gray, as they have a first child with the class "combinedColumn":
$('#combineDiv').children().has('.combinedColumn:first-child').css('background', '#ccc');