Didn't Alexander III make a comment to his wife in a letter to the effect that it was sad that Serge and Ella would never be able to have children? He seemed to know something that we don't know -- something that made it obvious to family members that there would be no children born to the marriage. I doubt it would be something like Serge being a homosexual, since it is hard to imagine that Alexander III would make sympathetic comments about that. I have read somewhere that Serge was impotent, which might explain the childlessness and AIII's sympathy, as well as Ella's silence on the subject. (This is all a bit personal, I realize, but then so is the whole thread. And in the case of reigning families, the personal can have profound political implications.)