joining datatables??

I want to join two datatables which are in a dataset, and then display the join table on a datagrid. I have tried to create relations in the dataset, but everytime the datagrid displays the parent table and it has that plus sign on the left side. I can't find a way to display the child fields. An example: There are three datatables. one contains the id number of a teacher and the id of the course taught by that teacher. the other table contains the id of the teacher and the name of the teacher. the last table contains the id of the course and the name of the course. I created the relations between the table that contains only the ids to the other tables, but I cannot find a way to join all three of them together for the display. Is there a way? Thank you.