During the Sunderum party it appears that Lobke has been dancing with Jelle all evening. He cares about her much more than as a brother. This to the great sorrow of Maam. She thought she was dancing with Jelle but turned out to have Aike in her arms. Sil looks at his son's attention to Lobke with great eye. that is not possible because he is his sister period. Quarrel is the result.