Does androgenic alopecia run in everybody in the family, or are some guys spared?

May be spared. The genes associated with increased risk of getting androgenic alopecia are primarily passed by your mother via one of her 2 x chromosomes or by one of her 2 chromosome #3. Therefore, brothers have 50 percent chance of getting the same chromosome. However, there is also an increased risk (about 2.5 x) of baldness derived from the father's y chromosome and/or chromosome #3.