Okay, little one, sippenhaft is a German word that means "kin liability." It's the idea that if one person in a family commits a crime, then everyone related to that person can be punished for it, even if they didn't do anything wrong.
So let's say your big brother gets in trouble with the law for stealing a candy bar. Normally, only your brother would get punished for that, right? But with sippenhaft, the police and government could come after your entire family, just because they're related to your brother. So even though you didn't steal anything, you could still be punished for it.
It's important to know that this idea is NOT fair or right. It goes against the idea that everyone is responsible for their own actions, not the actions of their family members. Sippenhaft was used a lot during World War II by the Nazis, who tried to punish entire families if one person in the family didn't support their ideas. It's something we should all remember to speak out against and make sure it never happens again.