See "A researcher has wrongly claimed co-authorship of my publication" in https://help.researchgate.net/hc/en-us/articles/14292798510993-Authorship for instructions how to correct this. But unlike this help page suggests, most probably it was not the other author himself who wrongly claimed co-authorship, but ResearchGate's automatic algorithm wrongly identified him as co-author and assigned your publications also to his profile. Unfortunately, this is a frequent problem in ResearchGate in case of similar names.