Data, Materials, and Software Availability. Anonymized data have been deposited in Open Science Framework (40) (https://osf.io/pmdeg/).Two separate but related literatures have examined familial correlates of male androphilia (i.e., sexual attraction and arousal to masculine adult males). The fraternal birth order effect (FBOE) is a widely established finding that each biological older brother a male has increased the probability of androphilia 20–35% above baseline rates. Other family demographic variables, such as reproduction by mothers, maternal aunts, and grandmothers, have been used to test evolutionary hypotheses that sexually antagonistic genes lead to androphilia among males, lowering or eliminating reproduction, which is offset by greater reproductive output among their female relatives. These proposed female fecundity effects (FFEs), and the FBOE, have historically been treated as separate yet complementary ways to understand the development and evolution of male androphilia. However, this approach ignores a vital confound within the data. The high overall reproductive output indicative of an FFE results in similar statistical patterns as the FBOE, wherein women with high reproductive output subsequently produce later-born androphilic sons. Thus, examination of the FBOE requires analytic approaches capable of controlling for the FFE, and vice-versa. Here, we present data simultaneously examining the FBOE and FFE for male androphilia in a large dataset collected in Samoa across 10 y of fieldwork, which only shows evidence of the FBOE.Portions of this work were conducted while S.W.S. was funded by a Joseph-Armand Bombardier Canada Graduate Scholarships (Doctoral) from the Social Sciences and Humanities Research Council
of Canada (Grant No. 767-2016-2485);
D.P.V. was funded during portions of data collection by a Natural Sciences and Engineering Research Council (NSERC) of Canada Scholarship-D3 (Grant No. 348679-2007);
P.L.V. was supported by grants awarded by the University of Lethbridge Research Development Fund (Grant
No. 13261), and a Discovery Grant from the NSERC of Canada (Grant No. 2020-04244)
