It's painfully obvious Iris is jealous of her identical twin sister Rose.The origin story behind their names helps us understand where Iris pain stems from as she believes her mother cast her eyes around the hospital room and named her after the first thing she saw which happened to be "spiky, unscented flowers" as Iris describes her namesake plant. Whereas Summer Rose was blessed with a special, meaningful name which was carefully thought through as it was prepared in advanced. She remembers various childhood memories right from her awakening thinking of when she swapped beds with her sister during their childhood. She is attached to the boat Bathsheba that Summer and Adam bought from her father. It's nice watching her observe other twins and sweet she relates to their invisible cues. Learning about their dad, his first wife who never turned up to the funeral although Iris missed the possible encounter and the and his new family added to the plot.