Finding the Artists that are married together

From Music Ontology Wiki

 1        PREFIX mo:      <http://purl.org/ontology/mo/>
 2        PREFIX rel:     <http://purl.org/vocab/relationship/>
 3        PREFIX foaf:    <http://xmlns.com/foaf/0.1/>        
 4        SELECT ?artist1_name ?artist2_name
 5        WHERE 
 6        {
 7            ?artist1  a mo:MusicArtist;
 8                      foaf:name ?artist1_name.        

 9           ?artist2 a mo:MusicArtist;
 10                    foaf:name ?artist2_name.        

 11           ?artist1 rel:spouseOf ?artist2.
 12       }