Today is Peyton Clark's 21st birthday! A bunch of your favorite celebrities have been wishing the I Didn't Do It actor a happy birthday today, including his sister Acacia Brinely. Since the web star doesn't have her last name associated with her accounts, some fans never even realized that they're siblings!

Click through the gallery to see more celebrities you may not have known are related, then let us know in the comments below which ones shock you the most.