My sister feels like a man and never accepted her female body, she lives with her girlfriend since she was 26 and now is 34. I always supported gay and lesbian but I can't understand this. What brings you to want to destroy your own body in order to appear like another sex? Is it biological, cultural or a mental illness? And mostly, can it be cured-fixed?

I am severely depressed due to this aspect of my sister and personally it's starting to destroy my already broken life.