If high blood pressure runs in my family, why was I spared?

All 5 of my siblings have high blood pressure, but I  do not. In fact, in my younger years, it was always pretty low.

I'm wondering if my diet, lifestyle, and living in a different part of the country might have had anything to do with it?  I left home as soon as I turned 18 and joined the Marine Corps, while the rest of the family stuck close to where we grew up.  I just think it odd that I'm the only one who escaped hypertension.