Cannot get value of a first TD in current row

My requirement is to have 3 check-boxes in each table row, and once the checkbox is checked, it will create a hidden input with the value corresponding to the first <td> of THAT particular row.

Here is a sample row:

<tr>
    <td>user1</td>
    <td>768.51</td>
    <td>4,680</td>
    <td>0</td>
    <td>0%</td>
    <td>0</td>
    <td><input type="checkbox" name=">1 year and <=2 years[]" onclick="createUserNameInput()"></td>
    <td>0.00</td>
    <td>0.00%</td>
    <td>1</td>
    <td><input type="checkbox" name=">2 years and <=3 years[]" onclick="createUserNameInput()"></td>
    <td>768.51</td>
    <td>100.00%</td>
    <td>4,677</td>
    <td><input type="checkbox" name="> 3 years[]" onclick="createUserNameInput()"></td>
</tr>

Once any of the 3 check-boxes are checked, this hidden input should be created. If 3 are checked, 3 inputs should be created. <value> of these inputs should equal the value of first <td> in THIS row, which is user1. Here is how I am trying to implement it (code is inconsistent but I just need to get it working first):

<script>
    function createUserNameInput() {
        // var input = document.createElement("input");
        // input.setAttribute("type", "hidden");
        // input.setAttribute("name", "user");
        // input.setAttribute("value", $(this).parent().siblings(":first").text()); // VALUE IS EMPTY
        // document.getElementById("main-form").appendChild(input);

        alert($(this).parent().siblings(":first").text()); // VALUE IS EMPTY
    }
</script>

I have referenced these previous posts but none of those solutions work for me. When I run alert(), value is empty - nothing is displayed:

1. Get first TD of THIS row
2. Jquery- Get the value of first td in table

Who can help? If it can be done without jQuery, even more amazing!