In androgen insensitivity, the X chromosome bears the abnormality that is responsible for the failure to produce the androgen receptor. If the mutation could occur after the splitting of the zygote, then you could have identical twins where one would be phenotypically female.
If the zygote were to lose the Y chromosome altogether, the resultant twins would be a normal male, and and abnormal appearing female, Turner's Syndrome.
Ain't Google grand. I certainly do not known if anything like this exists, but it is theoretically possible.
Well, it looks like it does. http://home.vicnet.net.au/~aissg/biographies/tony_briffa.htm
Jay
