XX is a female and XY is a male... the presence of a Y chromosome means the person is a male, no matter how many X chromosomes they have, if theres a Y, they are male...
XY - Normal Male
XYY - Jacobs syndrome ( i think )
XXY - Klinefelters? possibly...
XX - Normal Female
X0 or X- - Female, Turners syndrome
XXX - Superfemale
Also, because there are two sex chromosomes for each individual if a male has some type of disorder on his X chromosome from his mother, because he only usually has one X chromosome active with his Y chromosome, he will always show that disorder, where as if his parents has another child, and that child was a girl, say that she got the same X chromosome from her mum with the disorder on it, she may not present with the disorder because she has 2 X chromosomes and 1 only one of them is active at a time like her brother... she has 1/2 a chance that she will present with the disorder because her affected X chromosome may be inactivated and her X chromosome (which has no disorder) from her father may be activated instead...
Hope this helped, this is something my teacher told me anyways...
Aimee