Pre-note - I don't believe in a 'cause' of being gay or bi. I think identifying causes is a short step from identifying cures and, being very comfortable in a same-sex relationship myself, I don't think for one second that there's some kind of astrological 'queer switch'.
Having said that, in a few books I've seen mention of some astrological theories towards homosexuality or bisexuality. Aspects of Venus/Mars and so on. http://www.thegreenduck.com/ga/sample.shtml
gives a really good argument in saying that gender cannot be determined by a natal chart, nor left/right handedness, eye colour etc, so why would sexual orientation be?
But surely if a natal chart can indicate my sense of humour, for example, or that I'm liable to drug addiction, why not my attitude towards my own sex?
Sometimes astrology seems a little biased. I've come across reference to relationship astrology where x is 'the male' and y is 'the female'. To me this suggests that astrology can indicate heterosexual patterns - so why not homosexual?
I just wondered if anybody had any opinions, or any points of note in their own birthchart.