Bob and Erna actors

According to the trivia for this film, Ben Becker and Meret Becker are actually brother and sister. They could have definitely edited around the kiss scene so that it didn't actually happen, but they didn't and it went on for a while; at least it feels like it went on forever now that I know this tidbit of info, haha.

Even as an actor, there has to be a line drawn for something like that, no??