Birth order in a contemporary sample of gay men

The birth order of a contemporary North American sample of 97 gay men was quantified using Slater's Index. For the 84 probands with at least one sibling, the results showed a late mean birth order compared with the expected value of .50. Additional birth order indices derived from Slater's Index suggested that the mean later birth order was accounted for more strongly by the proband's number of older brothers than by his number of older sisters. The present findings constitute a replication of a series of recent studies and add to the growing body of evidence that birth order is a reliable correlate of sexual orientation in males.