I just found this kind of old paper on the gentics of GID. The conclusion is:
"Overall, the results support the hypothesis that there is a strong heritable component to GID. The findings
may also imply that gender identity may be much less a matter of choice and much more a matter
of biology."
I have a great-grandfather that had GID, but none of my 2 daughters or my 3 son seem affected. How about you?
Kate D D
Behavior Genetics, Vol. 32, No. 4, July 2002 (© 2002) p251
The Heritability of Gender Identity Disorder
in a Child and Adolescent Twin Sample
Frederick L. Coolidge,1,3 Linda L. Thede,1 and Susan E. Young2