Unfortunately, Instagram doesn't exactly give us the green light on requesting usernames. Here is what the company has to say on the subject: "If a username you want is being used by an account that seems inactive, you can choose an available version of the username. You can add periods, numbers, underscores, or abbreviations to help you come up with a username that's not already in use." Of course, this doesn't mean you can't try, at least. It won't hurt to contact Instagram and request a username you think is inactive.