I would have to dust of a few brain cells but im sure when we touched on hair and eye colour in genetics it was a bit more complicated than one pair of genes. I think there are about 5 with some that are closely located on the chromosone. Some combinations are therfore rarely seen – like light ginger hair and dark brown eyes etc.
I am one of a pair of children from two very dark brown haired parents I was blonde as a child and my brother was dark, we have both ended up with the same dark brown hair.
Of my four (fathers dark blonde) one is an adult with dark blonde hair, but the other three look like they will end up dark. Even though one was blonde when he was small, one was already dark (and hairy!) And the third. . . . If I hadnt seen him come out I would have questioned whether he was mine as he definitely had a red tinge! (Nothing against it it was just a shock!)