Finding Duplicate in XML Attribute

In my SQL Server DB,I have table with XML Attribute. The XML that goes in it is like the sample below:

    <Rows>
          <Row>
               <Name>John</Name>
          </Row>
          <Row>
               <Name>Debbie</Name>
          </Row>
          <Row>
               <Name>Annie</Name>
          </Row>
          <Row>
               <Name>John</Name>
          </Row>
    </Rows>

I have a requirement that i need to find the occurrence of all rows where the XML data has duplicate entries of Name. For ex. above we have 'John' twice in the xml. I can use the exist xml statement to find 1 occurrence, but how can i find if its more than 1.

Thanks.