The least likely explanation for this would be that they're training at different intervals, or one is training harder than the other.
The most likely reason is that the way the other person's genetics are most people cant gain muscle as well as others because of disease or their body structure.
Hope this helped!
The rounded mass of fatty tissue lying over the joint of the pubic bones, in women typically more prominent and also called the mons veneris<span>.</span>