Hal and Harper, two codependent siblings living in L.A., are doing their best to navigate long term relationships, friendships, and situationships. When their Dad announces he's having a new baby with his girlfriend, Kate, the two are forced to consider the current state of their lives, as well as their complicated childhood. While exploring the trauma of their past, and the dramatic changes of their present, Hal and Harper and Dad chart the evolution of their family, while discovering the ways their intense bond has shaped the ways they interact with those they love, for better or for worse.