Gaining muscle for Person A vs Person B

Can someone who has very little to no muscle gain faster than someone who has a decent amount? This is assuming they're both newbies to lifting and both their training/nutrition are on point. Like for example:

Person A - Male, 5'7, 120 lbs @ 10% bf, 20 years old /Person B - Male, 5'7, 140 lbs @ 10% bf, 20 years old

Since Person A has much less muscle and is further away from his "genetic potential" can he gain faster than Person B? I always figured underweight people could gain much faster than those who aren't....