As a matter of fact, as a photographer, when taking pictures for other people, the biggest distraction comes from the sun, especially strong and burning sunshine, since they often do work outside. So, my advice for you is to buy a pair of polarized sunglasses for your brother, and the design and type is not a problem, what you should consider the most is the sunglasses' function to protect his eyes.
Personally, i don't think we can suggest you the best sunglasses for photographers. You may prepare several pairs for using different situation. If you gonna to go a dark light places, you can choose sunglasses with yellow lenses. The sunglasses will enhance the contrast so as to allow you get clear vision in that environment. But yellow lenses sunglasses may cause color distortion, you need prepare other sunglasses when you stay in strong light places such as grey sunglasses. Anyway, if you work outside, you'd better choose sunglasses with polarized lenses which surely help you.
If your brother is a photographer, you'd better choose the polarized sunglasses which could protect the eyes from the strong lights which could damage the eyes. Compared with other common sunglasses, the polarized sunglasses own special function which could do good for your eyes. The effects of the polarized sunglasses are to effectively eliminate and filter beam of scattering light. It can make the light go through the optical input eyes and become the visual image. Thus, the vision is clear and natural as the principle of shutter shade. At last, the light has been adjusted into synthetic light and enters indoor and the natural scenery looks soft and not dazzling. You could choose such type of polarized sunglasses, like the oakley brand which is more suitable for your brother.