High number of twins in Cuban capital district baffles scientists, as locals blame everything from genetics to a sacred tree

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 neighbours 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 road nearly free of traffic, as tropical music floats out from behind graceful porches and balustrades. But if you spend any 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 nine-year-old. "We're twins and we love living on this block because we have twin friends."

Tamara Velazquez, who's been busy raising six-year-old identical sisters Asley and Aslen, said: "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.".

"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 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.

Twins Fe Fernandez (l), and her sister Esperanza, aged 65. Photograph: Ramon Espinosa/AP

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.

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 neighbours 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, such as Mercedes Montero, mother of 21-year-olds 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."