They are not related

I just can't grasp why are people saying it's weird. Like childhood friends trope is soooo popular, so if you feel this is not right than any childhood friends to lovers are not right.
They both know their whole life they are not siblings. They never considered the other one as sibling. In their childhood they were using each other and were trying to survive next to each other. Most of the time they were housemates with bad fate. So I am here for the romance between childhood acquitainces who developed feelings for each other. If you are feeling that's wrong, I have a news for you. You made the problem in your mind, which is telling something about your perception... The relationship is ethicaly and moraly, even by law alright.