I don't mean to be rude, but that's not really true. because to say it is is to put the cart before the horse (which is not true).
I personally am very impressed with the expression of the protagonist from VN "Proud Father" - "if for the happiness of my daughter I need to have sex with her, then so be it."
that is, the daughter's happiness is at the forefront, and the way to achieve it is unimportant.
in general, I'm looking for consistency in stories, not inconsistency (this is a horse). and what kind of story it might be - it doesn’t matter at all, even if it is an incest story (and this is a cart). and in the cart, everything should serve to ensure that the horse easily and naturally drags the cart from the start to the final.
and when the horse does not take out - and disassembly begins, where is the problem.
although if we touch on the topic of incest, then it’s interesting what clicks two people? if in the morning they woke up, say, mother and son, and in the evening they go to bed as husband and wife. this very "click" should be natural and logical, so that there is no unbearable desire to shout in anger "I DO NOT BELIEVE!".