Can you tell me if a person has a specific genetic disorder, is every other person on earth that has that same genetic disease related to that person?

Generally no: While we all share genes with our ancestors, many genetic diseases arise spontaneously in different populations. Mutations happen all the time in our germ line. If it hits a gene that has an important function it causes a disease. Some genes, or areas of genes are more predisposed to spontaneous mutations (e.g. Due to their large size). This a way same mutation can occur in different populations.