What is the punishment for someone who engages in obscene acts with his sister?

If the question is about a brother sexually harassing his sister, this is a grave evil and its perpetrator is a dayyuth (a cuckold/pimp, implying one who condones immorality among his kin). A dayyuth will not enter Paradise. Parents must care for their children and raise them well religiously. The daughter must dress modestly in front of her brothers and avoid being alone with her harassing brother or allowing him to touch her, while also monitoring what their children watch on the internet and satellite channels.