Hi, welcome to BYC!

Your pic doesn't show much other than size. How old are those boys? So ya, just off size alone, I'm thinking the white one is probably a cockerel as well.
For comparison look at the combs. If they are the same age and all you would see significantly less comb on a girl. You will have to hold the crest back. My girls started laying at 6 months old. They have a little bump of a comb. But they seem almost half the size of yours.
