Alright, let's get this out of the way. I'm 20 years old - 5'9" 135lbs - and have been 'training' 6 times a week for almost 3 months. This is the first time I've trained since high school wrestling.
I cannot gain fat. I'd like to, but my body won't let me. I heat up to 110+ degrees while I sleep and burn carbs like a monster. I eat more than anyone I know - not an exaggeration. (No, I don't have tapeworms.)
That being said, there is some uneven development of the lower external obliques near the pelvis. The left side is bulkier (which I like) than the right side. The abs are pretty close to identical. I'm doing 3 sets of leg/knee raises and 3 sets of bicycle kicks 3 times a week. I make sure to do an even number of lifts and kicks for each side of my body.
Check out this picture and let me know if there is anything I can do to improve even development. (I don't need a lecture on genetics, if it's not possible then that's that.)