Radio Buttons and Parent/Children

How would I go about writing this?

In a Javascript Function radio(obj) write code that if id=”radGroupParentY” is clicked then loop through all radio buttons below it and set the attribute checked=”true” to all their children id=”radGroupChildY” I can’t just say checked because it is within an XSL and it needs to be checked=”true”

As an example I only put 2 children but their could be more.

Parents
<input type=”radio” class=”NavMnuSecHeaderTitle” value=”Y” onClick=”radio(this)” id=”radGroupParentY” name=”clid123rid124″>Yes
<input type=”radio” class=”NavMnuSecHeaderTitle” value=”N” onClick=”radio(this)” name=”clid123rid124″ id=”radGroupParentN”>No

Children
<input type=”radio” class=”NavMnuSecHeaderTitle” value=”Y” id=”radGroupChildY” name=”clid126rid125″>
<input type=”radio” class=”NavMnuSecHeaderTitle” value=”N” id=”radGroupChildN” name=”clid126rid125″>

<input type=”radio” class=”NavMnuSecHeaderTitle” value=”Y” id=”radGroupChildY” name=”clid136rid135″>
<input type=”radio” class=”NavMnuSecHeaderTitle” value=”N” id=”radGroupChildN” name=”clid136rid135″>

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