Forum:Treated as monsters

Have a question, with monsters like Harpie Queen, and Harpie Lady 1,2, and 3. So are we allowed to have 3 of each in our deck or does them being called Harpie Lady prevent that? I remember in an old game I had, I couldn't do that, for example I could have one Harpie Queen, and two Harpie ladies but couldn't add more, was this just a glitch or is that an actual ruling?