Additional links of interest:

1.CDC Facts about Hemophilia

2. A Pedigree of Hemophilia in the Royal Families of Europe: Male bleeding disorders were predominant in the royal families of Europe. Because of frequent intermarriages between royal families, the hemophilia trait was prevalent. Alexis, son of Nicholas II, last tsar of Russia, was thought to be a hemophiliac. The student familiar with Russian history knows that Alexis's hemophilia was influential in bringing down the Russian royal house.