Uh-oh, Claire did some research...
Well, my previous comment about twin studies got me to do some research. While I found no studies of crossdressing (per se) in twins, there have been a number of studies of "transgenderism" in both monozygotic (identical) and dizygotic (fraternal) twins, and in these cases "transgenderism" seems to mean "transexualism", or at least GID. There is a paper in the International Journal of Transgenderism (I didn't know that existed!) that summarizes the known case histories when at least one twin was transgendered. Some fascinating results. For identical twins born male (total of 39), in 13 pairs (33%) both twins transitioned, or at least identified as female, while in the other 26 only one did. For fraternal male twins, in only 1 of 21 cases did both identify as female, while in the other 20 only one did. The numbers for female identical twins were lower: there were 27 cases of at least one FtM transition, in 8 of which (23%) both transitioned. In none of the 15 female fraternal pairs did both individuals transition. Overall, both twins transitioned in 20% of the pairs studied. :whew!:
Now if you are still with me, (:yawn:) what does this mean for us? I think one thing that is clear is that a recessive gene is probably not involved, as some have suggested. If so, all, or at least a large majority, of identical twins (which would have the same genes) would have been TG. The author does conclude that there is likely a genetic basis for GID, but this does not mean that it is an inheritable trait. This does seem to cloud the issue of the effects of hormonal exposure in the womb. Shouldn't both individuals be exposed to the same hormones?
Bottom line: we shouldn't be concerned that because we are CD, our kids will be. And I still believe that my TG is something I was born with.
If anyone is interested, here is a link to the paper:
http://www.tandfonline.com/doi/abs/1...2#.VHm4A9LF_Ss