" What no one then, of course, knew was that as female children of the tsaritsa, one or all of the sisters might be carriers of that terrible defective gene – a hidden time bomb that had already begun to reverberate across the royal families of Europe. Alexandra’s elder sister Irene – who like her was a carrier and who had married her first cousin, Prince Henry of Prussia – had already given birth to two haemophiliac sons. The youngest, four-year-old Heinrich, had died – ‘of the terrible illness of the English family’, as Xenia described it – just five months before Alexey was born. In Russia they called it the bolezn gessenskikh – ‘the Hesse disease’; others called it ‘the Curse of the Coburgs’.66 But one thing was certain; in the early 1900s, the life expectancy of a haemophiliac child was only about thirteen years.67 "

― Helen Rappaport , The Romanov Sisters: The Lost Lives of the Daughters of Nicholas and Alexandra