Gotta love it when a character with complex gender expression is introduced in a straight romance manga and the comments devolve into whether if trans people are real or not. Happens literally every time.
To be specific, children of cousin couples are two times more likely to have birth defects, but this increase correspond to an increase in probability from 3% to 6% for an individual child to have birth defects. Roughly, from 1 in 33 in non-related couples to 1 in 17 in cousin couples.
The real...