It also has a bit of attitude and chases the other two around some times. I've caught it chest bumping one of the other chickens too :0
Edited by muscake - 1/14/16 at 9:23pm
Combs don't start to develop until the bird is reaching reproduction maturity. Males mature and develop a lot faster than females. A pullet won't really begin to have significant comb growth until they are getting close to laying eggs. Males will be fully mature by about 14 to 16 weeks old. Pullets are mature until 20 to 25 weeks.
Given the size of that comb, at only 11 weeks, it's most definitely a boy.