Going back to the original post of this thread, the photo shows one chick significantly larger than the others. It appears that individual is about one week older than the others. That's all it signifies at this point. It's too early to judge gender.
However, watch the comb development on all of the chicks. An early indication of a cockerel is a yellow tinted comb when compared to washed out pink color of the pullets' combs, which are barely visible until closer to three or four weeks.
By age four weeks, a cockerel may have a more defined comb and it will be yellow-orange in color. By age six weeks, the comb has noticeably developed beyond the pullets' still inconspicuous combs and it will be a red-orange color to the pullets' still very pale pink.