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"Moral Flexability" the line from the main character in Gross Point Blank on why he became an assassin

And I still think it fits the way I was envisioning play him anyway.
Genetics:
Your world, your genes

And it keeps the society rolling like it needs to. I'll say the the d'Toussaints produce above-average daughters consistantly, or have enough flukes that there is at least that perception.
I will say that you are missing two possible elements here. One is that mitochondrial DNA is not the only direct genetic carryover, the daughter always gets one X chromosome. Or did you mean un-recombined, and thus direct from the grandmother?
In any case, I could easily see in the Rowaini environment, genetic pressures that would allow other cases. As I said though, you world, your genetics, just offering some additional possibilities.
Consider X chromosome inactivation. Different regions of mammalian X chromosomes get "turned off" so as not to duplicate them. There is certianly enough genetic pressure on this population that if mother's genes are most important to beauty, and beauty is a fitness adapation (which you said it is, since ugly or plain daughters are often killed), there could evolve an selective adaptation where the mother's X chromosome is more often left on and the father's inactivated.
Additionally, the synergy between a polygenic trait and sex-influence could produce the effects you want. Again, the genetic "fluke" you speak of, a stunning daughter born to a plain mother is well nigh impossible under a straight genetics linkage.
But consider a polygenic line with say 4 alleles, and thown in sex-linkage and the 4 alleles in 16 combinations, becomes 32 when you account for sex-influence. And the best part, the male and female phenotypes can be completely unrelated (Str/Con for men and beauty for women). And that's from a single locus!
Sorry ,I get carried away. I should probably disclose that I have a Ph.D. in Molecular Genetics so these kinds of things tickle many of my fancies
Again, your world, I am not arguing with how you have things set up, the world-structure takes all precedent, I am merely suggesting a few changes that would explain the genetic phenomena a bit more robustly.
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