sess.createSQLQuery("SELECT p.name as personName, c.name as catName, k.name as kittenName
FROM people p, cats c, kittens k
where p.id = c.id and c.id = k.id
and p.name like '%Tom%")
.setResultTransformer(Transformers.aliasToBean(PersonDTO.class)).list();

public class PersonDTO {
   private String personName;
   private List<Cat> cats;
}

public class CatDTO {
   private int catName;
   private List<KittenDTO> kittens;
}

public class KittenDTO {
   private String Name;
}