The girl said that she found out that she and her brother liked everything related with incest, stories, photos, videos, etc... It took some time to try to start a conversation with her brother about the topic but one day she finally got the courage and she was glad she did, they started to share their finds about the subject. After some time the topic came up naturally when they were alone and both wanted to go a bit further but none of them knew how the other would react, but it did append eventually. Now they don't miss a chance every time they are home alone.