It was a more general type question, I left out specifics on purpose. Does it matter if a twin did medium grip pull-ups vs close gripped biceps? If 25% of his upper back work consisted of the latter, will he have bigger biceps than the twin who does curls?
How would the fact of whether they were obese or skinny make a difference in the results to their biceps?
Like I said, it's a general question along the lines of compound vs isolation exercises for a discrete bodypart. But if you want specifics, let's say for the back-training twin, 12-15 sets consisting of 6-12 reps divided evenly between dumbbell rows, wide grip pull ups, t-bar rows, and rack pulls. The biceps-training twin does 9-12 sets consisting of 8-15 reps divided between dumbbell curls, hammer curls, and cable curls. Average weight, 1 year of training experience, they can do 10 bodyweight chin-ups.