I had two bantam rooster that started to crow between 8 and 9 weeks. My meat birds roosters will sometimes start to crow right before they are processed at 8 weeks. I would say yours is overdue in the crowing department.
12 weeks is right on target, depending on whether he has competition, my silky boys are 3 mth old and have just started to crow having a few days break in between. Im sure he will fire up, he is just practising and possibly embarrased!
My Ameraucanas made initial noises at 12 weeks - so I knew they were roos - but didn't really get into it until 15-16 weeks.
My buff rock and buff orpington roosters both started crowing on the same day at 15 1/2 weeks old. My barred rock rooster I adopted hasn't crowed yet and he is about 22 weeks old.
I had 1 little cockerel that started crowing at about 3 weeks old. All of my others didn't start till much later. Sometimes it just takes a while. Jayare