Evans Otieku, so many journals recommend from authors to suggest some reviewers upon submission; however, it is not necessary for the journal to follow the list suggested by authors. In my opinion, as long as no conflicts of interest exist, this shouldn't compromise ethics.
Good question, I agree with the remark by Evans Otieku that editors have only the option to choose from suggested reviewers. I personally always check the suggested reviewers (whether they for instance were also co-authors or are working in the same department). I also never choose more than one of the suggested reviewers. But sometimes it is good to have such suggestions, especially if we talk about very specialized articles. in such cases it is sometimes difficult to find two to three good reviewers. To answer your question, I guess that it is ethically to suggest good specialists as reviewers (not your friends), and it is the professional responsibility of the editor to check appropriateness of the suggested reviewer.
In my case I almost always chose reviewers who are well established in the field of the study and who I have no connection personally or professionally. Also I check the journal editorial board so ensure atleast a couple of the are close enough to the research submitted. This ensures that apart from the reviewers I have suggested , they would also know exactly who to chose for reviewing this paper. Thus I almost always chose journals based on editorial board instead of metric like JIF simply coz this formula has earned me some of the best quality reviews, has pushed my knowledge boundaries and importantly improved the paper to a standard eligible to be appreciated by knowledgeable peers/ experts.
Some high quality journals ask authors to put forward a few people considered to be appropriate reviewers on grounds of expertise but also to suggest reviewers who, for whatever reason, you would not want to referee your piece. There might be a long-standing feud or such a fundamental difference of outlook as to make impartial assessment impossible. In addition, such journals usually reserve the right to follow their own preference in reviewers, so that your article is seen by people beyond your known research circles as well as by researchers who might be sympathetic through prior acquaintance.
Evans Otieku Usually they do not contact your recommended reviewers. Only in case no other reviewers accepted to review your article, they would contact your recommended reviewers.
Dear Evans Otieku in our field of research (chemistry) it is quite normal and absolutely not unethical to recommend potential reviewers for a submitted manuscript. In fact, most chemical journals nowadays require that 2-3 possible reviewers are named during the electronic submission process. Some journals even ask for up to 5 names. If you don't suggest any reviewers at this stage, the submission process will stop. You can even oppose certain reviewers, e.g. when they are direct competitors in your field of research. It is only unethical when you suggest reviewers who have joint papers with you or are your personal friends. Suggestions should only be based on research expertise.