The rates of heterosexual marriage are increased in families where there are older sibs versus children with fewer older sibs. These are not huge effects but they increase probabilities by a small amount. Some heterosexuals may cohabit, some remain single.

Even in convenience samples, the birth order effect for homosexuality is not large, explaining only about 1% of the variance. This study suggests that in an entire population the birth order effect goes away.

I think you are making an assumption that is contradicted by this study.

I think we can agree that if there were something about birth order itself that influenced whether a gay person were likely to marry, then married gay persons would not be representative of gay persons as a whole when discussing birth order. In other words, birth order would differentiate unioned from ununioned gays.

It might initially seem counterintuitive that birth order in married gays and unmarried gays may be different It might seem that I’m grasping for reasons to discount your observation. However, the abstract of the study itself states that birth order seems to impact marriage decisions:

“Heterosexual marriage was significantly linked to having young parents, small age differences between parents, stable parental relationships, large sibships, and late birth order.”

We know that “late birth order” is not a trait related to being straight. 90 plus percent of the population cannot have the attribute of “late birth order”. Thus clearly birth order has an influence on the decision to marry, at least for straights.

Given that birth order has an impact on straight marriage, wouldn’t you agree that it is not reasonable to dismiss it as having no impact on gay marriage? The impact may be different (as is the rural/urban split) but surely it can’t be dismissed offhand.

Thus we can see – or so I believe – that any observations about married gays that discusses birth order cannot be extrapolated to the gay population at large.

It’s somewhat like saying that we can observe whether unmarried gay people wear wedding rings by looking at what married gay people do. It seems as though there’s a built-in bias.

So the quotes about “these homosexual men” can’t be extrapolated to anything beyond “these homosexual men”.

I’m sorry if I was confusing. I wasn’t suggesting that the gay married people were not a subpopulation of the gay people. Just that they are probably not a representative subpopulation from which any conclusions could be derived.

If I read this correctly, all that can be determined from this study is what type of people marry. It would seem that the type of straight person that marries is somewhat different than the type of gay person that marries. This suggests to me that the same social forces result in different responses determined by whether the subject is gay or straight.

For example, in the country there seems to be greater social pressure for straight people to marry. But this same culture seems to discourage gay people from marrying (I suspect that would also be true in the US as well). However, this observation could not then be used to assume that people are less likely to “become” gay if they are raised in the country. That would be an extrapolation that does not seem to be evident. It is probably more likely that gay persons are less likely to ruffle feathers in a small town by getting married.

That’s all I’m cautioning, that a look at marriage not be taken to be a look at orientation.

We know that married straight people are not representative of straight people in general. For example, in the US they are more likely to be religious, live longer, more likely to have a “nuclear family” dynamic, and (I believe) more likely to be politically conservative than are unmarried straight people. To look at married straight people and then make assumptions about all straight people would be very poor social science indeed.

I don’t think it a stretch to believe that gay married persons differ from gay unmarried persons in Denmark. The “more likely’s” are probably not exactly the same, but its fair to assume that they exist and probably are much more extreme.

So to look at married gay Danes and say, for example, that birth order observations can be extrapolated to all gays, would be rather presumptive, I think.