Sorry, forgot to say that is two different chicks.
Rooster in question is the second one.
It's not 100% for sure yet, but I would be very surprised if the one with a mostly black chest didn't turn out to be a cockerel.
From above they look identical with only a slight difference in tail carriage/feathering, but it really depends on what they are doing at the moment. I honestly can’t tell the difference from that viewpoint.
The pictures were taken a few days ago and they will be 10 weeks tomorrow.