At 17 months, Triniti and Ghabriael are chubby-cheeked twins, born 11 weeks early at three pounds each and now healthy and a joy to their parents.
But when their mother, Khristi Cunningham of Akron, Ohio, takes them in public, the babies get a lot of second looks and questions.
Triniti has ebony-colored skin and all the classic dark features of an African American, but "Gabe," as his parents call him, is ivory-white with steely blue eyes and blond hair. He's now 10 pounds heavier than his sister, but it's their racial identity that gets people scratching their heads.
"People ask, 'How did it happen?' Are you sure they are twins?" said Cunningham, 29. "We get a lot of stares, and I am sure people make comments behind my back."
Their mother is white and their father, Charles Cunningham, is black.
"I don't know how it happened," said Cunningham. "They are fraternal twins, so they aren't any closer than if they had been born years apart. Ours just happen to have the same birthday."
Geneticists say racial differences involve many genes and are more complex in determining looks than those for eye color, but the startling difference between the twins raises an interesting question about how mixed-race families are viewed in a country that is increasing biracial.
Even the Cunningham's pediatrician was baffled by the black and white babies.
"She asked if they were identical twins," said Cunningham. "That was the last time we went to see her."
Having a black and white twin is "no big deal from my viewpoint," said Dr. Ronald Bachman, retired chief emeritus of the genetics department at Kaiser Permanente Hospital in California.
"I share a common trait with most medical geneticists," he said. "We don't know a hell of a lot and don't pay much attention to skin color and eye color, although we are asked at cocktail parties all the time."
As for the Cunningham's pediatrician, Bachman says only a careful study of the placenta by the obstetrician or a DNA test can definitively determine if twins are monozygotic (identical) or dizygotic (fraternal).
Identical twins develop from one zygote that splits and forms two embryos. Fraternal twins are two eggs that have been fertilized by separate sperm.
In fact, identical twins are not exactly alike, genetically, according to Bachman. "There are scant variations between the two, who grow up in different places in the uterus and as they grow in time have various somatic mutations [that are not passed on]. There are gene changes within them."
Because the United States is such a diverse country racially, couples can carry an assortment of genes from multiple racial backgrounds. Skin color, according to Bachman, is determined by "multiple genes, not a single gene."
"An assortment of genes go into the egg and sperm to get skin color," he said. "This family is no different. The twins are just like siblings in biracial families."
The Cunninghams met in 2006, while working in a juvenile prison in Columbus three hours away from their families. They later moved, got new jobs in an auto plant and married.
They knew carrying the twins would be challenging. She lost a son the year prior to conceiving the twins because of an incompetent cervix.
The goal was to get to 24 weeks when the babies would be viable outside the womb, but they held on for an additional month and were delivered in September 2009.
At first their developmental milestones were a bit delayed, but now they are "well adjusted and caught up," according to their mother.
Although the Cunninghams pay little attention to the skin color of their babies, the world is not color blind.
Before they were married, the couple's co-workers had difficulty accepting their biracial relationship. They were ultimately fired from that auto plant where there were "huge racial overtones." Charles was reinstated only after the Ohio Civil Rights Commission investigated.
Later, neighbors in the rural community where they lived called Khristi Cunningham "the little white girl Charles had married."
When the story of their black and white twins was told on the blog, Mixed and Happy, some readers reacted negatively.
"They asked if we'd had genetic tests done," said Cunningham. Another remarked, "How can you do this to your kids?"
"No one gets to say if they are black or white," said Cunningham. "It's not a choice and to me they are perfect and will grow up to be loved.There's too much hate. People should be more worried about whether you're a Republican or a Democrat."
Biracial Children Banned From Class Office
Last year, the same blog first reported a story about middle school in Nettleton, Miss., that restricted who could run for class office by race. The policy was a holdover from late 1960s desegregation orders.
Brandy Springer's daughter, a sixth grader of mixed white and Native American heritage, said her 12-year-old girl came home distraught because she would not be allowed to run for reporter, a position slated only for black students.
Springer also had another son of mixed white and Native American heritage and two younger children, who are mixed white and African American.
After a story ran on ABCNews.com and repeated calls to the school board and administrators, Superintendent Russell Taylor issued a statement revoking the policy that reserved class officers for specific races.
Incidents like these are not uncommon, even today when one in seven marriages is between spouses of different races, according to the Pew Research Center.
And for the first time, the 2010 Census allowed Americans to check more than one box to describe their ethnicity, results that are expected in March.
According to a recent report in The New York Times, the current group of college students is the largest group of mixed-race ever in the United States, fueled by immigration and intermarriage, and their numbers are expected to rise.
The editor for Mixed and Happy, Suzy Richardson, is white, married to a black firefighter and lives in Gainesville, Fla. The couple has four children aged 2, 4, 9 and 12.
"My oldest son has green eyes. Two of my children are dark and two are light," said Richardson, 34 and a former magazine editor.
Richardson grew up with a black stepfather and biracial sister who was "condemned by both sides -- black and white people."
When she met her African-American husband, she said, "I remember a black girl saying to me I would never date someone of another color."
Pregnant with their first child, she and her African-American husband were even denied seating in a small-town Florida diner.
Richardson said she started her blog after learning in 2009 about a Louisiana judge who refused to sign a marriage license for a biracial couple because he was concerned, "they might one day have these mixed-race kids that would not be accepted by either side and tend not to be happy."
So angry, she solicited stories from other biracial families and sent a Christmas card to the judge with photos of their "happy" children. The blog was born and soon, she intends to provide news pertinent to biracial families.
"I realized there was a need for them to connect and unite," said Richardson.
Now, she tells her own children that they are neither black, nor white, they are both.
"We still get looks, but I don't mind the questions at all," she said. "Grownups have a need to categorize, but not children."
Still, during the 2008 election, when Americans proclaimed Barack Obama the first black president, Richardson's children were confused.
"They struggled with that," she said. "They said, 'But Mom, I thought he was biracial like us.' The world thinks you have to choose one side, who you are. We call him a biracial president and tell them you have two sides, Mommy and Daddy. They don't have to choose."