I am sure you can understand that I am not an expert on the genetics, physiology and psychology of such people. I believe that people who, unfortunately, have been born with such genetic abnormalities ought to be handled with compassion and love. I am afraid that many will blame such people for things they cannot control. It would be tragic of Christians made life even more difficult for "intersexual" people by being judgmental or by forcing legalistic definitions and categorizations on them. Let me be honest. I really do not know how to best help people who are born with gender not well defined. I believe that probably it is best for them to somehow choose one gender or the other and do their best to live life with this identity. Bottom line, the Bible does not give a commandment which we can apply in a black and white way to this issue. I do not believe that people would have even understood the terms we are using and God did not address the question in the Bible. Therefore it is our job as Christians to find a compassionate and biblical way to help such people navigate life. It seems likely that people with no defined gender ought to remain unmarried because of the problem which would be created for their spouse, as you suggest. I think that I would give this advice, but until I am faced with a particular case, I do not want to give a hard and fast "ruling" which I believe I am not in a position to give.
To summarize; I suggest compassion.