Issac

Because he wasn't technically human before he was turned, he aged at a much slower rate . Which is an aspect of his species*

*Species: Anthro (note, this is my version of an Anthro, which is a humanoid that can shapeshift into one specific/(on rare occasions multiple) animal form. When well practiced they gain complete control over their transformations. They also have a much longer lifespan than humans, and members of the species often age at different rates from each other, so years aged does not equate to physical appearance. The rate at which they age often slows down even more once they reach maturity)

Physical characteristics amongst Anthros varies, but generally humanoid forms display pointed ears. Other animalistic features can be represented on individuals as well, such as eyes, fur, ect. But prominent features such as these will always be present, and cannot disappear while in s humanoid form.