Radio buttons are a special kind of field, since they come in groups, sharing the same name but having different values. The TMT Validator validates a set of radio buttons with the same name as a unique entity. So, inside a set of radios, we can define the validation attributes only once (if you specify attributes with conflicting values, the last one wins):
<input name="drink" type="radio" class="boxes" value="Nicole" tmt:required="true" />
<input name="drink" type="radio" class="boxes" value="Kate" />