SHE had no uterus.. and probably an over sized "cliterous".. and SHE had probably never been examined by a physican. I babysat for a child with ambiguous genitalia back in the early 1960s. It happens.
She is only 13. Surely doctors who delivered her would have checked her and reported something was not right at the beginning. How can the mother not notice as she grew up in diapers.
Pediatricians don't examine babies for a uterus.. and it He looked like a girl, why would the mother think otherwise?
It wouldn't be a fully formed penis. It wouldn't even look like a penis. It would have looked like an enlarged clitoris at birth, perhaps thought to be swelling as a result of the birth, perhaps. No one would have been any the wiser until he hit puberty.