Regarding eye colour and geneticWatch
From my basic remembering of high-school science :
B is dominant
b is recessive
BB = brown eyes
Bb = brown eyes
bb = blue eyes
So it's entirely possible for everybody in a family to have Bb type brown eyes if one parent has passed down their B and the other parent has passed down their b...
until one day both parents might pass down their b and them bam suddenly a blue eyed child is born.
I know that's basic but that's how they explained it when I was a kid.