People generally play this close to the vest, but it seems word always gets around when coworkers are receiving raises. So if you’ve confirmed that other employees are asking for and receiving raises, and you’re either at their level or do better work, then that can be a positive sign to ask for a raise of your own.
The only thing we’ll caution you on here is not to reference the raises of other employees in your request. A raise should be about you, your work, and your potential future value to the company that makes you a worthwhile investment. Going into your boss’ office and saying “Well Sally got a raise and I do twice the work she does” just sounds whiny.