There are exceptions, but there is a definitive correlation. Talked with some very experienced doctors about this. Somebody email Leo and Longevity about this. He has OCD about finding research and I'm not interested in it enough as I have full head of hair in my late 40's, done many cycles. While anecdotal, my mothers father had full head of hair at 80. My father was bald as was his father.
According to Bosley, "There are many myths regarding the relationship between genetics and hair loss. One popular myth is that hair loss in men is passed down from the mother’s side of the family while hair loss in women is passed down from the father’s side; however, the truth is that the genes for hair loss and hair loss itself are actually passed down from both sides of the family."
On the other hand, according to the Amarillo Hair Restoration Center (AHRC), Hair loss is hereditary, but it’s probably not your dad’s fault. Men inherit the baldness gene from the X chromosome that they get from their mother.
Baldness may be influenced by a number of other factors as well, including age, health, diet, hormones, seasonal changes and climate. Trauma, stress and anxiety may also adversely affect hair growth because they can lead to reduced blood and oxygen supply to the scalp, which is essential for maintaining a healthy head of hair.
My thought is when I fellow realizes he's losing his hair, it causes great stress and anxiety which accelerates the process.