Multiple radio button groups in one form

Set equal name attributes to create a group;

<form>
  <fieldset id="group1">
    <input type="radio" value="value1" name="group1">
    <input type="radio" value="value2" name="group1">
  </fieldset>

  <fieldset id="group2">
    <input type="radio" value="value1" name="group2">
    <input type="radio" value="value2" name="group2">
    <input type="radio" value="value3" name="group2">
  </fieldset>
</form>