Hello I face this problem and my thinking is that after sharing our problem. You will provide me a good suggestion. I create relationship between 3 tables with 1 primary key. I share our problem with attachment. tables relation's does work correctly.
Please provide more information. What data do you (want to) keep in the database / tables Please provide some examples and let us know what exactly the problem is with the relations
After seeing your tables its look like Table1 Table2 should be the msater table and both have there primary key.... Table2_1 should contain forign key for the both i.e relation between the both primary keyss.....
From the information you've provided, it doesn't seem you have a problem. If you want an answer for a problem, it would be good if you write what your problem is...
I also don't quite understand what's the problem exactly. You pretty much just described your database structure and nothing else... provide much information if you want help.