Okay, so, quite obviously, I am a transgirl. I'm mexican & as the stereotype goes, my parents are stupid & bred like rabbits. I'm the 10th baby. My older sibling has also been gender dysphoric since a young age & I believe him whole heartedly. He's 23 & has never acted on his desire to be a girl even though he is clearly as feminine as can be. Not flaming, but feminine, like a girl. Whether it be from his geriatric personality, desire for plants, pottery, cooking, cleaning, etc. He is a girl & I genuinely can not see him as a boy even though he presents as one. He does identify as homosexual although as said before, he is nothing close to flaming, just EXTREMELY feminine. I came out at a pretty young age & if I do the math correctly, he was around... 19 when I came out as transgender. He's always been very supportive of it obviously because he feels transgender too. He IS a girl & there's no doubt about that. My mom would say otherwise but she's very religious & she even calls me her son, with my makeup, boobs, & hair almost touching my butt.

Another thing I've always noticed is that he has chronic depression (I think from gender dysphoria) & anxiety. He feels awkward & out of place & I've always tried to help him go through with transition but I think he's very scared. He's reaching the short end of the stick in terms of transition & he knows it. The only problem is that gender dysphoria isn't treatable unless with HRT. People try to cope but it eventually comes back to haunt them later in life & end up transitioning way later. I always tell him that the earlier you start, the better the results & he knows but he's just very scared I think..

Anyways, do you think it could be genetic?? What are the odds that two siblings could both be transgendered? Oh ! Also, I remember seeing a study that for every boy a mother has, it becomes 25% more likely that the next will be gay due to the mothers body being able to feminize the embryo better. Oddly enough, he's the 4th boy, & I was the 8th boy & final child born. Coincidence?

I know something about cows where as the mother first had a boy then a girl that the young one is noticably too 'male' for a female cow,...

But for humans... I really can't say...
I'm no world-class proffesor in genetics...,
sadly, my loan would be unreal tho

Anyways as for your brother it's good to support him or her.

But don't push it tooo much if you know what I mean

I personally know a trans-woman whose son also transitioned to female. There was a trans-woman on these forums a year or two ago whose daughter transitioned to male.

So it does happen

Yes, this can happen. Apparently my father was like me. I've no idea how common it is though.

Possibly could have a genetic component. Current thought is that it is caused by incomplete masculinization of the brain due to hormonal mistiming in utero, or androgen insensitivity, both of which could have a genetic basis (just speculating) or it could exposure to external chemicals with estrogenic properties. It is now known that DES a synthetic estrogen used until the 1970's could overpower testosterone and is estimated that one quarter to one third of DES sons are transgender.

Lots to speculate on because you know many of us would like to know if there was/is an identifiable cause.

Wishing you and your brother the best.

Hugs 

Not exactly the same, but my little brother came out as gay years before I ever came out transgender. My parents only had two boys and when I talked to my sister she said she's not sure what if she likes guys or girls sometimes. I always found it kind of interesting that all three of my parents children basically came out non heterosexual.

Supports my theory:

When there is baby girl, the womb is still filled with (prog)estrogen(e). If the next baby is born very soon after the first birth, (impregnated weeks after the 1st birth) these hormones might still linger in the womb. So if the time between births and impregnation is small, it might affect the hormonal balance a bit. Not sure if it is true though, would love to see a study about it, because I think it affected me. I was born right after my sister, we even look like each other when we were kids. People always thought we were twins, and have a mere 13 month age difference.

There is a known effect for males, that birth order affects sexuality. The more older brothers a man has, the more likely he will be gay.

http://en.wikipedia.org/wiki/Birth_order#Sexuality

I've wondered this myself as my son is also transgender.  He had no idea about me when he came out and began his own transition so no possibility of any kind of environmental influence.

When he came out to me I can't tell you the feelings of guilt I went through thinking it was somehow "my fault".  I scoured the internet for any information about the possibility of this being a hereditary condition and found absolutely nothing.  I also did find that there really are no studies that have been done on this (at least there weren't at the time).  It would be an interesting study though, I'd be interested in the findings.

I don't feel guilty any more btw, we are who we are and everyone is beautiful in their own way. 

I don't know anyone else in my family who's gay/trans or just non heterosexual but I always wondered if my body image issues were genetic since my uncle definitely has has some body image issues and has had some cosmetic surgeries. I don't think my uncle is anything other then straight but he is also very religious so pretty sure he would die before coming out as not straight. but thats just speculation.