Is sexual orientation determined at birth?

I believe that it is; there was even a recent, very interesting study
of how men are more likely to be gay depending on how many older
brothers they have. The researchers even studied adopted children and
depending on how many older biological brothers they had the results
were the same, so the orientation was definitely established in the
womb. Here's a link to an article about the study:

http://www.newscientist.com/article/mg19125584.900.html

The answer and comments to this previously asked question may of interest:
 
Subject: Is male homosexuality a physical problem or psychological problem? #1
http://answers.google.com/answers/threadview?id=137712