Whats up with the scenes of Dennis and Dee being flirty with eachother?

I've been rewatching all the seasons recently before the next season airs. Ive noticed several weird scenes where Dennis and Dee are clearly too "comfortable" with each other for a brother /sister relationship. When they are dancing with each other in the dance marathon is the one that stands out the most. In the Pop Pop episode Dennis and Dee are huddled together where Dennis has his arm around her and Dee is touched right up beside him while drinking. There are other scenes as well. I wonder if this was something the actors chose to do to make them seem extra dysfunctional . They should make an episode where Dennis or Dee WANT to hook up. And pull a Game of Thrones on the audience . WEIRD!!