It is not normal to consider competitors as interested party of an organization. I would consider competitors as interested parties if, for example, they could be partners in research and development, or in the introduction of sectorial practices, or if they could be subcontracted for certain processes.
The following material will provide you information about interested parties:
- ISO 9001 – How to determine interested parties and their requirements according to ISO 9001:2015 - https://advisera.com/9001academy/blog/2015/11/10/how-to-determine-interested-parties-and-their-requirements-according-to-iso-90012015/
- free online training ISO 9001:2015 Foundations Course – https://advisera.com/training/iso-9001-foundations-course/
- book - Discover ISO 9001:2015 Through Practical Examples - https://advisera.com/books/discover-iso-9001-2015-through-practical-examples/