I found an answer as to why the hemophia factor might have been ignored in a book called 'Nicholas and Alexandra', chapter 12, page 150-151.
The author writes:
"... Why, then, did it come a such an overshelming shock to Alexandra that her son had hemophilia?
"One reason suggested by the late British geneticist J.B.S. Haldane is that although the genetic pattern was known to doctors, this knowledge never penetrated the closed circles of royal courts: 'It is predictable,' wrote Haldane, 'that Nicholas knew that his fiancee had hemophiliac brothers although nothing is said in his diaries or letters, but by virtue of his education, he attached no importance to this knowledge. It is possible that they or their counselors consulted doctors. We do not know and doubtless will never know if...the court doctor counseled against marriage. If a distinguished doctor outside court circles had desired to warn Nicholas of the dangerous character of his approaching marriage, I do not believe he would have been able to do it, either directly or in the columns of the press. Kings are carefully protected against disagreeable realities ... The hemophilia of the Tsarevich was a symptom of the divorce between royalty and reality.'
"... In marrying and having children, hemophilia was considered one of the hazards royal parents faced, along with diphtheria, pneumonia, smallpox and scarlet fever.
"... In that era, every family, including royal families, had a long string of children and expected to lose one or two in the process of growing up."
That makes sense. Finally!
Thanks everyone for your posts.