Nissel's second book, Mixed: My Life in Black and White, is a comedic look at growing up as the child of a biracial couple.

Born to a biracial couple - his father is black, his mother white - Christie grew up in Seattle.

Dizygotic twins from biracial couples can sometimes be mixed twins, which exhibit differing ethnic and racial features.

The sight of a biracial couple seems to draw out the worst of the racism that is here, Ms. Wireman said.

"We're getting hitched," said Curtis Woolbright, a plaintiff who said he had taken part in the suit because his parents, a biracial couple, had to fight to get married.

A mellow, biracial couple answered and greeted him warmly.

The majority of black students at Harvard were West Indian and African immigrants or their children, with some others the mixed-race children of biracial couples.