The sister woke up from the penetration, saw that it was her brother's dick who fucked her and did not refuse to continue.

Just by entering the room to his sleeping sister, the guy was probably in a state where he not only did not want to, but also did not consider it necessary to think about the consequences and simply took the pussy of his sleeping relative. Waking up two minutes after the cock had already made her pussy wet, the girl saw that it was her brother who crossed her river but did not refuse to continue.