I put this in both places:
Randomly researching something for a hobby, I found this article on the family of Tsar Nicholas II:http://www.sciencemag.org
Highlights from the article (from my perspective):
?The Tsarevitch (Alexei) had hemophilia Type B, which is far more rare than Type A;
Alexandra (which we knew) was the carrier;
Of the four daughters, only Anastasia was a carrier.
Helen Rappaport's book on the four daughters of Nicholas II was very specific on the point that Nicholas had put into motion a plan to name his eldest daughter as his heir after Alexei (or assuming Alexei's death before Nicholas'). Had Alexandra not gone totally around the bend (pretty well documented and the extended family really noticed it at Cowles in 1909), Olga could have been married and settled (possibly abroad) prior to the second revolution (Feb 1917) and even a mother of a child without hemophilia. Same for Tatiana on that score.
The sheer cluelessness of the last 20 years of the dynasty is just breathtaking.