[Pseudoscience-is-malarkey (OP)]

It used to be said that homosexuality was caused by society and a person's upbringing, i.e., "it's society's fault for your condition..." But most of us in the West now know we're born gay or straight. But other identities such as foot fetishes, pedophilia, coprophilia, lactophilia, cfnm, or violent acts that are required or preferred to achieve arousal, I think we can say these are not identities people are born with. Freud started this mode of thinking, and it has become prevalent in pop culture these past couple of decades- that is having a fictional character with a weird sexual identity that is the product of some childhood incident. I don't know.

[Petrochemicals]

I have great problems with sexual identity, my sexuality does not contribute to my self identity what so ever although it may in other people's eyes. Sexual identity is something that is in the animal kingdom, I try to aim a bit higher. Maybe this is because of child hood trauma, perhaps I should walk around with no trousers on.
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[alancalverd]

Beware of loose terminology.

Sexual identity (what you are) is determined, for almost everyone, at conception. Nearly everyone is either XX or XY.

Gender preference (how you choose to behave) can be expressed at any time. Since dress and behavioral norms are societal, it must be a product of environment and experience: we are not exposed to societal norms in utero, and they are not entirely consistent between societies.

Sexual preference (homo, hetero or bisexuality) tends to be expressed around or after puberty, making it impossible to state in a single instance whether it is inherent or acquired. However if it is inherent, one would expect to find a strong correlation of homosexual preference among siblings. I am unaware of such data but if it is available, it might support  the underlying genetic hypothesis of

most of us in the West now know we're born gay or straight.

even if most of us are in fact unaware of it.

One tends to associate "fetishes" with males, "fantasies" with females, but since they involve external experiences and activities that do not occur in utero they must all be products of environment  and upbringing, not genetic.

[Petrochemicals]

Sexual preference (homo, hetero or bisexuality) tends to be expressed around or after puberty

There are said to be signs before hand.

However if it is inherent, one would expect to find a strong correlation of homosexual preference among siblings

It could just be your mother had a fad on soya beans or any other hormone infuening scenario.

[Pseudoscience-is-malarkey (OP)]

Sexual preference (homo, hetero or bisexuality) tends to be expressed around or after puberty, making it impossible to state in a single instance whether it is inherent or acquired. However if it is inherent, one would expect to find a strong correlation of homosexual preference among siblings. I am unaware of such data but if it is available, it might support  the underlying genetic hypothesis of
Quote from: Pseudoscience-is-malarkey on Yesterday at 15:41:30
most of us in the West now know we're born gay or straight.
even if most of us are in fact unaware of it.

I knew my preference before puberty. This seems to be true with gay people as well. They often say something to the effect of "I knew early on I didn't feel the same way about [opposite sex] as my friends."

[alancalverd]

Which is why I said "expressed at or around....", and "early on" is not a number or even a physiological milestone. Homosexual experimentation of some degree is very common at an early age, but rarely expresses as a strong preference before puberty.

[Petrochemicals]

But are such experiences pre pubesant a perversion, paedophilia produces pedophiles.

[alancalverd]

I think folk nowadays would distinguish between sexual identity (the question  asked), which most would interpret as gender identity or homo/hetero preference (since true "identity" is in the genetic hardware), and perversion. 

[Petrochemicals]

I think folk nowadays would distinguish between sexual identity (the question  asked), which most would interpret as gender identity or homo/hetero preference (since true "identity" is in the genetic hardware), and perversion. 

That sort of answers the question, if it is a product of your upbringing it is a perversion. But it doesn't answer what 'sexual identity' is meant to be in the OP.