Answer
(Fatwa: 967/810/B=1432)
If your brother has only feminine signs (though they are incomplete) or he the feminine sings dominate, then in this case wearing female clothes and marrying a male shall be lawful for her. However, it will be necessary to explain the situation to the second party. Yes, if he is khunsa mushkil i.e. he carries both the masculine and feminine signs and no side can be given preference or no sign is found, then in this case his nikah is not lawful at all.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband