
Fiction doesn't and will not equate to real life, yes, that's a fact. However, it can influence real life. Just like @Bluemoonie said, it can make messed-up stuff feel normal, and that's harmful.
May I remind you again of how incestuous relationships were done in royal bloodlines to keep their lineage pure back in the old days? It messed up their kids and their affected their quality of life.
So yes, I would like to reiterate that although your statement IS correct and factual, people pushing sibling-ships, or for a general term—incestuous ships, into media CAN and WILL influence people in the real world.
Why do ppl think it’s ok to ship literal siblings in the name of just being fiction ?