National Geographic : 2012 Jan
who were both into sports. "But then Lily went out for track and won her hundred meter," Kirk says. "And I came back to that nature versus nurture thing." e push and pull between genetics and fam- ily life is never far from their minds, the couples say. "We like to think we're making an impact as parents," Allyson o ers. But then in the middle of a conversation Lily will roll her eyes exactly the way Gillian does, and Allyson is suddenly re- minded of her daughter's twin. "It's like, whoo!" she says. "Sometimes it will stand the hairs up on the back of my neck." e ird Component at Lily and Gillian seem so similar, despite being raised in di erent families, underscores the genetic heritage that identical twins share. But for two brothers in Maryland, the situation is just the reverse. Despite being raised in the same family, these identical twins couldn't seem more di erent. What could be so powerful that it trumps the combined e ects of nature and nurture? "I saw a cumulus congestus cloud at recess today," Sam says, making conversation as he waits for his brother, John, to get home from school. "It was very big. en it broke up into a nimbostratus." A bright-eyed six-year-old with glasses, Sam sounds like a professor in a meteorology class. Clouds are his latest passion, his mother says. Before that it was trains, space, and maps. Lately, he's been working his way through a child's en- cyclopedia, gathering facts like a squirrel hoard- ing nuts, as she puts it. e twins are both in rst grade, but they at- tend di erent elementary schools, so that John At one and a half years old, Declan Conrad (at right) weighs ten pounds more than his identical twin, Finian. e boys began growing at di erent rates inside the womb, where they had unequal access to blood ow and nutrients from a shared placenta.