I've never owned chickens but I think the big one is a boy (Sunny) and the little one is a girl (Greta). There is a mix of all different ones but as for the Barred Rocks there are large and small sized ones at the farm. I'm really sorry the pics aren't better.
It's a bit too soon. Basically, here's the deal on Barred Rocks. Males carry two barring genes, so they feather out with bright, wide, vibrant bars on a back ground that almost looks to be dark charcoal.
Females will feather with one barring gene, which gives the barring a less "pop" to the eye and the background will be almost black.
Finally, at 6-7 weeks, the cockerels will sprout pink to very red combs and wattles under their beaks. The pullets do not normally show any red combs and no wattles until much closer to laying. Side by side? It is very obvious. Just give it a little time.
Sorry everyone for not responding sooner, I've been swamped with other things and forgot that I post this thread. I found out the sexes of the chickens, they're a bit older now and have more feathers. The large barred rock (Sunny) is a boy and the small barred rock (Greta) is a girl.
Here are some updated pics of them, including a new little girl called Polly (black rock):
The reason Sunny is in the house is because the lighting was better.
He's gotten so big now and he's as cuddly as ever!