Actually, I posted the preprint a while back, but did not get to writing about it. This is a culmination of several project students who attempted to replicate the findings from Buunk (1997) on birth order. Across three measures, Buunk (1997) found that firstborns reported less jealousy than laterborns. Across four samples, we did not find substantial evidence for this claim. We also performed several robustness checks - a tentative conclusion is that we should likely ignore birth order effects in this context and move on,… .
Read the preprint here