That DNA string seems to have an effect on cogenital traits as well, at least in my Karen run, making full use of divine marriage (I married sister, daughter, aunt, whoever just had the genius trait, the low marriage pool (Few zoroastrians and can't marry other religions) meant no geniuses otherwise), after a few generation my current ruler made 9 kids, 4 geniuses, 1 inbred, rest normal. Not that I'm complaining, mind youNo, it's definitely possible and has happened before:
https://forum.paradoxplaza.com/foru...reenshot-thread.585791/page-988#post-21063123
https://forum.paradoxplaza.com/foru...-game-says-my-just-born-son-is-inbred.770750/
The issue is that DNA strings are relatively short and it's possible for wife/husband to have a similar one by pure chance:
https://forum.paradoxplaza.com/forum/index.php?threads/dna-mechanics.749853/#post-16752587