I don't think you can know for sure due to their age. I have 16 Barred Rocks that are 11 weeks old today but I still can't tell yet. I've read that if their color is mostly light they are males. All of mine are fairly dark wit the darker bands dominating so I'm keeping my fingers crossed. Now I'm no expert by a long shot, but the birds in your picture look lighter colored than mine, so if I were a bettin' man, I'd lay odds you have boys. But seriously, take that with a grain of salt because I'm only working on my first flock at this point.