See "A researcher has wrongly claimed co-authorship of my publication" in https://help.researchgate.net/hc/en-us/articles/14292798510993 for instructions how to correct this. But unlike this help page suggests, most probably it was not the other author himself who wrongly claimed authorship, but ResearchGate's automatic algorithm wrongly identified him as the author and assigned your publication to his profile. This is a frequent problem in ResearchGate in case of similar names.
Please note that you wrote to the ResearchGate community, not to the RG team. But it is not worth writing to them because they will give the same advice.