There isn't anything wrong with creating multiple "city-pages" on your website targeting different city names. Just be careful, because if there isn't enough unique content on them that is valuable to the user, they could be labeled as Doorway Pages, which are against Google's guidelines. Phil Rozek has a great guide full of ideas for content for these pages.
What is not allowed is creating multiple listings for the same business in Google My Business. Google will remove the listings if they catch them and can possibly suspend the user's account as well. Using addresses of relatives to create these listings would also be against Google's guidelines and would be defined as a fake listing.
I would only suggest creating multiple subpages for the location if they are targeting different keywords (products/services). For example, if you have a location for an insurance agent then it might make sense to have 2 subpages, one targeting auto insurance and another targeting home insurance. However, if the location just really offers one service, like a hotel, then it doesn't make sense. I've seen chains do this and often Google only ever ranks the main location page and not the subpage because they are all targeting the exact same thing and the content is almost the same.