The world's oldest conjoined twins died last week in Pennsylvania at the age of 62.Lori Schappell and George Schappell died April 7 at the Hospital of the University of Pennsylvania, according to obituaries posted by Leibensperger Funeral Homes of Hamburg. The cause of death wasn't detailed.Born Sept. 18, 1961, in West Reading, the twins had distinct brains but were joined at the skull.George, who had spina bifida and was 4 inches shorter, was wheeled around by Lori on an adaptive wheeled stool.The Schappells both graduated from a public high school and took college classes.George went along for six years as Lori worked in a hospital laundry. She then gave up the job so her brother could launch a country music career.Conjoined twins occur once in every 50,000 to 60,000 births when identical twins from a single embryo fail to separate. About 70% are female, and most are stillborn. Only a small percentage are joined at the head, with nearly three-quarters joined at the chest and others at the abdomen or pelvis.The oldest ever documented were Ronnie and Donnie Galyon, who died in 2020 at age 68. Eng and Chang Bunker, the 19th-century conjoined twins who became known as "Siamese Twins" and gained fame as a circus act, lived to be 63.