Study the whole dna bonding thing. It is possible for two brown haired indivualls to have a child with red hair. If it is given by both parents. It could be a hidden trait that they carry and it is not dominant in them, but would be in the child if a less dominate trait, such as blonde, appeared.
Also, if you are white, it is possible that you have "black" blood in you. Unfortunatley our ancestors had slaves and there was a lot of sex crimes committed. One of your great, great, great, great... Grands could of been of a different race and their traits was just never dominate.