Please don't get too worried about this, but, if you can, try to integrate your discussion based on an idea rather than on the texts. For example, say that the question is, "Belonging to a group can bring both challenges and rewards". To what extent is this your view based on your prescribed text and TWO related texts of your own choosing?
I would write on the challenges in the prescribed text and those seen in one of my related texts. Then I would write on rewards to belonging seen in my prescribed text and my second related text. So that pattern would be
Introduction/thesis statement
Idea 1-Prescribed text
Idea 1 - first related text
Idea 2 -my prescribed text.
Idea 2-second related text
Conclusion.
Just remember, it is not specifically the texts you are comparing, it is the ideas on belonging in the texts and how these are revealed by the different composers. There are other structures you can use. The most important aspects for this question are -your ideas about belonging, textual detail supporting those ideas from the texts and your ability to keep to your thesis and the question asked. All the best.
