So far your either born male or female and being registered that way but to November a new law will take place who makes it posible to be registered male-female or X. this law is made with intersex people in mind.

the person can in the future become male or female, or stay X in the registration, however if the person stay X there can be trouble since german do not have same sex marrige it could be difficult to get marrige if your neither register male nor female. as well as traveling with X can be troublesome in some areas.
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German artical:
http://www.sueddeutsche.de/politik/geschlechter-im-deutschen-recht-maennlich-weiblich-unbestimmt-1.1747380

English artical:
http://www.spiegel.de/international/germany/third-gender-option-to-become-available-on-german-birth-certificates-a-916940.html

I love this. I hope it happens everywhere eventually.