China's capital saw double on Saturday as Beijing opened its first festival for twins, attracting hundreds of look-alike siblings, a rare sight in a society where birth control rules limit most urban families to one child.

Twins in matching cowboy hats, sweaters or scarves mingled, chatted and performed on stage at the government-sponsored event in a Beijing park. A pair of men played a saxophone duet and younger twins danced and sang.

Participants ranged in age from 69 to 4-month-olds in a double stroller. Organizers said 500 sets of twins, including some from abroad, signed up to attend the four-day festival. Fifteen-year-old triplets from eastern China also showed up.

"Now with family planning, every family is only supposed to have one child. So we're lucky," said Wang Yanren, one of the trio of teenage girls.

Chinese, who wish newlyweds "double happiness" and entrepreneurs "double fortune," look on twins as a sign of good luck. A boy-and-girl pair is called a "dragon and phoenix," a reference to two traditional symbols of prosperity.

Rules imposed two decades ago in hopes of slowing the growth of China's vast population of 1.3 billion people limit urban couples to one child and those in the countryside to two. But twins and other multiple births are exempt from heavy fines imposed for additional births.

Many participants said that having a twin sibling meant added emotional support in a society of single children -- isolated "little emperors" -- who Chinese officials worry are growing up maladjusted.