If you have a personal or professional relationship to an author that could potentially appear to be a conflict of interest, then you should decline to review the manuscript. Reviewers should avoid even the image of impropriety in the review process. If you discover a conflict of interest after accepting a manuscript for review, then you should discuss the issue with your editor.
For more on the ASHA Journals reviewer conflicts of interest policy, please visit the Peer Review Policies page.
You can also learn more about conflicts of interest and other ethical dilemmas in peer review in the ASHA Journals Academy PREP Development Modules, Module 4: Publication Ethics.