Hair Genetics - Where does it come from?

[jonnykino]

Okay, so I have a question about hair genetics.

I've always heard that your hair genetics are based on your mother's father, but after reading around that's apparently wrong? So is it based on your father? Or is it just simply... unpredictable?

I'm curious, because, my uncle (he married my aunt... my mum's sister) through marriage started to lose his hair when he was in his 50's. He's now 70, and he's bald. His eldest son, who I think is about 38, has thinned a bit up top, but he has enough hair on his head to more or less cover up the thinned bit, and if you saw him in the street you wouldn't consider him bald. In fact, the majority of his hair is thick and dark. His second eldest son has a full head of thick, dark hair, no thinning or recession. However, around his temples the hair is turning grey. But no hair loss. He's 36. My uncles third son (again, with dark hair), who is nearly 30, his hair has thinned out a lot on top, far more than his eldest brother. Then my uncles youngest son, who is 23 has a full head of coarse, curly, dark blonde hair.

My grandfather had thinned a bit at the front, but he had enough at the front to part his hair over to the side, before he passed away aged 79.

My two other male cousins, who had a different grandfather, both have a full head of hair, and they're in their 40's.

So I just don't understand how hair genetics works.

Can anyone explain? Or is it just too unpredictable, and nobody knows?