Python: Append two XML tags

I have this XML file and I'd like to read some data out of it using Python's xml.etree :

<a>
   <b>
      <AuthorName>
         <GivenName>John</GivenName> 
         <FamilyName>Smith</FamilyName>
      </AuthorName>
      <AuthorName>
         <GivenName>Saint</GivenName> 
         <GivenName>Patrick</GivenName>
         <FamilyName>Thomas</FamilyName>
      </AuthorName>
   </b>
</a>

The result that I wish to have is this :

John Smith
Saint Patrick Thomas

The thing, as you may have noticed, is that sometimes I have 1 GivenName tag and sometimes I have 2 GivenName tags

What I did was this :

from xml.etree import ElementTree as ET
xx = ET.parse('file.xml')
authorName = xx.findall('.//AuthorName')
for name in authorName:
    print(name[0].text + " " + name[1].text)

It works fine with 1 GivenName tag but not when I have 2.

What can I do?

Thanks!