Twin-Tuition: Meet the Twins

As part of "Nightline Prime: Beyond Belief" series, we take a look at twin-tuition, the unspoken, telepathic communication between twins. The number of twins born today has doubled since a generation ago -- from three to six million sets of twins a year. Fraternal twins, like siblings, share 50 percent of their DNA, but identical twins share 100 percent of their DNA. A survey of 5,500 twins found that 1 in 5 identical twins said they have experiences some form of telepathy between each other. J.J. Pearce High School in Richardson, Texas, set the Guiness world record for the most sets of multiples in a single grade: 10 pairs of twins and a set of triplets. Tune into "Nightline Prime: Beyond Belief" Wednesday, June 29 at 10 p.m. ET/PT. (Amy Gutierrez/ABC News)