Responses
I agree.
They're Dad is the Heavenly Dao which is basically a natural phenomenon from our human pov. They don't share "blood" per say nor were they "raised" with the human siblings logic.
Some of the readers are thinking it was incense, although they are right as both the MC and ML are brothers as they were made by the 'god', but in gods eye I think just like on greek gods, even though they are siblings it is okay to get married and have children between sister and brother. So its just the same happening to both lead characters. ╮(￣▽￣)╭
Sorry for my english and Its just my opinion and interpretation.