JavaScript with a few modifications:
function deleteRow(btn) {
var row = btn.parentNode.parentNode;
row.parentNode.removeChild(row);
}
And the HTML with a little difference:
<table id="dsTable">
<tbody>
<tr>
<td>Relationship Type</td>
<td>Date of Birth</td>
<td>Gender</td>
</tr>
<tr>
<td>Spouse</td>
<td>1980-22-03</td>
<td>female</td>
<td><input type="button" value="Add" onclick="add()"/></td>
<td><input type="button" value="Delete" onclick="deleteRow(this)"/></td>
</tr>
<tr>
<td>Child</td>
<td>2008-23-06</td>
<td>female</td>
<td><input type="button" value="Add" onclick="add()"/></td>
<td><input type="button" value="Delete" onclick="deleteRow(this)"/></td>
</tr>
</tbody>
</table>???????????????????????????????????