marginally significantp = 0.053
The within-family effect was not significant averaging across zygosity (beta = -0.126, p = 0.303), but there was a marginally significant interaction of the within effect by zygosity (beta = 0.468, p = 0.053), such that there is a marginally significant within effect for MZ pairs (simple effect beta = -0.354, p = 0.055) but not DZ pairs (simple effect beta = 0.114, p = 0.469).