[MargaretR]

Transgender issues aren't rare. You just don't hear about them often, because those affected rarely have the courage to change to , what they feel, is a lifestyle which expresses their true identity. I met some of them during my career.

Some people are assigned the wrong gender at birth due to the size of sex organs not being within what is considered the 'norm'.

Others can be hermaphrodite or 'intersex' (they are not the same)

Wikipedia pages explain these phenomenon.