"incest!" it's not they're not related by blood and tbh this is more like childhood friends to lovers since their ages are not that different.
Correct me if I got it wrong but do you mean blood relationship as in like, siblings? This is just my personal thoughts but maybe because even if it is a homosexual relationship, it is still considered as blasphemous like it is in a hetero relationship. Any homosexual person is still a normal human being. So think about it, isn't it quite strange to have a relationship with someone who you share a blood with? Unless they're one of the greek gods or something. (I'm not mocking the greek gods, don't attack me please) ╮( ̄▽ ̄)╭
OMFG POSSESSIVE GF, NOW THIS IS WHAT I WANT
Same