How do you know when your sister is on her period? When your dad's dick tastes like blood
What do you mean?  Are you saying that something like this has really happened?
You know what I mean.
If you meant this as a joke, then you should be aware that people who have suffered trauma will not find it funny, and could suffer real distress from hearing such a thing.  And if you were being serious, then you should definitely alert the authorities about the kind of abuse that is happening.