[Caged Great]

Here's how genetics works

Blue eyes is a recessive gene, Brown is a dominate gene

Say both your parents have brown eyes, it is possible that you can have blue eyes

...................................from father
............................ Brown............................Blue
From mother- Brown- Brown Brown ................ Brown Blue
...................Blue-...Blue Brown.....................Blue Blue

Where there is a Brown, the child will have brown eyes, but there is one that has two blues, therefore it will have blue eyes. There's a 25% chance of that happening and a 75% chance that it will have a blue gene