---------- Movie 1 Megatron is the main villain, After His death it is stated that He and Optimus Prime are brothers, Thus Viewers assumed that Megatron (In some way or form) was a Prime. Movie 1 main villain(as far as the viewers were concerned)= a prime ---------- they are not brothers, they are refer themselfs as brothers as in "Brothers in arm" or that they were once friends, sometimes friends reffer themselfs as brothers. the original ide4a was indeed to have them as siblings, but bay and the writers got rid of the idea, plus the reason why Megs is working with the fallen is so he can be a Prime, so thats means Megs is not a prime