If my whole family has blue/green eyes, why does my youngest brother have dark brown eyes?

Question: If my whole family has blue/green eyes, why does my youngest brother have dark brown eyes?
- Keywords:
  eyes,
  genetics,
  inheritance
Asked by helloimholly to Nick on 12 Mar 2014.
- Nick Goldman answered on 12 Mar 2014:
  
  Although it seems simple, eye colour is actually a complicated genetic characteristic that is not totally understood. It could be that your family has lots of different eye colour genes, and it’s just chance that most of you come out with the same colour eyes. Or it could be that your youngest brother has a brand new mutation that means he really is different from the rest of you.

Question: If my whole family has blue/green eyes, why does my youngest brother have dark brown eyes?