Havana – Some say it could be something in the water. Others point to a tree with mystical significance for locals. Maybe it's just chance.
But neighbors all marvel at the 12 sets of twins living along two consecutive blocks in western Havana, ranging in age from newborns to senior citizens.
"We were the first ones," said Fe Fernandez, 65, who wears her gray hair closely cropped.
"It's incredible!" said her identical sister, Esperanza, who shares the same features but whose black-dyed hair falls to shoulder length.
At first blush there isn't much about 68-A Street to mark it as different from anywhere else in the city. Children play ballgames in the rugged road nearly free of traffic, as tropical music floats out from behind graceful porches and balustrades.
But if you spend any amount of time here, before long you might think you're seeing double.
"Hi, I'm Carla, and this is my sister Camila," said Carla Rodriguez, a smiley, bespectacled 9-year-old. "We're twins and we love living on this block because we have twin friends."
"I never expected it. No fertility treatments. It was my first pregnancy, and at five weeks they did an ultrasound and I was carrying twins," said Tamara Velazquez, who's been busy raising 6-year-old identical sisters Asley and Aslen.
"It's a lot of work. It requires a lot of patience," Velazquez said. "They are very active and dominant, although each has a different character."
Ten of the twin sets here are identical, and the other two fraternal. None of the mothers interviewed by The Associated Press said they had received fertility treatments, although most said multiple births run in their extended families including relatives living elsewhere. None of the families are related to each other.
All but one of the sets were born into these homes, and the lone newcomers moved into a house that was vacated by twins who moved to Spain. Others have died or moved away over the years.
"Twins leave, twins come," Fe Fernandez joked.
The 70 or so houses on these two short blocks are home to around 224 people, extrapolating from national statistics on average household size.
That works out to about one set of twins for every 20 people. Historically the rate has been about one per 80 live births, though experts say that's rising globally, primarily in developed countries where fertility treatments are more readily available.
It's impossible to say what could be behind the high number of twins here, or whether there is any cause at all.
Scientists say a variety of factors play into twin births, such as race, the mother's age and diet. Western Africa, from where many Afro-Cubans can trace their ancestry, has significantly elevated rates of twinning.
Meanwhile statisticians caution against the human tendency to seek patterns of serendipity in a random world.
"Something could definitely be there, it could be a combination of various factors," Andrew Gelman, a statistics professor at Columbia University, said via email. "In addition, opportunistic counting can make a small and natural pattern appear larger."
For example focusing on these two blocks without considering other surrounding ones, he added, "puts the spotlight on a small subset."
While there's been no scholarly study of the twins on 68-A Street, they nonetheless consider themselves part of a special community. Some look to faith for an explanation.
"There are neighbors who are religious. Many say it's the Siguaraya tree, which people ask for things and is in one of the homes," Fe Fernandez said. "The people believe in it strongly."
Leafy and embellished with delicate white blossoms, the Siguaraya is considered sacred in the syncretic Afro-Cuban Santeria faith and is associated with a powerful "orisha," or spirit.
Others, like Mercedes Montero, mother of 21-year-old Xavier and Lorena, chalk it up to the luck of the draw.
"It's a very big coincidence," Montero said, "one of those strange things in life."