In time dilation, does the "aging" referenced include biological/ physiological aging? for example, in the identical twin concept, is it possible for the twin who travels to space and back to have actually aged so much that by the time he returns his brother is dead of old age? in other words, does time dilation affect physiological processes?
Every object has its own frame of reference. So, time dilation only means that, for this case, the twin in space is aging slower according to the twin that is still on Earth. However, according to the twin in space, he is aging normally in his frame of reference. In other words, yes, time dilation does affect biological aging. It just affects it differently depends on whose perspective you're with.
Time dilation affects time itself, which means that it affects absolutely everything. For the twin that traveled away and came back, literally less time will have passed for him than for the twin back on Earth. So he will have aged less, his shoes will have worn out less, the turbines on his spaceship's pumps will have rotated fewer times - everything.