Is it normal to have cracks in your teeth?

I was at the beach and just got finished eating lunch. I didn't have a mirror but I had my digital camera so I was looking at my reflection on the camera screen to check if I had anything in my teeth after eating. It was around noon so the sun was shining directly overhead and when I angled the camera screen a certain way I could see the sun shining straight on my teeth and I saw a crack in my front tooth running diagonally from top to bottom of the tooth. The other people that were at the beach with me could see the crack in my tooth too when the sun was shining directly on it. When I got home I couldn't see the crack unless I shined a flashlight on my tooth. I shined the flashlight on my mom and dad's teeth too and I was able to see that they both have cracks in their teeth as well. The cracks in all of our teeth are only visible when light is shined directly on them. I'm only 20 years old and I never noticed the crack in my tooth until now. I've been going to the dentist every 6 months for my entire life and the dentist has never mentioned anything about it. Also, I want to get braces but now I'm scared that my teeth are too fragile for braces! I don't want my teeth to crack or something when the braces are moving them! Is it normal for me to have cracks in my teeth at this age? Is it safe for me to get braces?