The way that Jack, Rose, and Nine feel far more like a poly trio in late Season 1 rather than any sort of love triangle is INSANE. The vibes are FERAL and IMMACULATE. The kisses in Parting of the Ways. The sharing-story banter in Boom Town. The flirting. "Buy me a drink." "Continue on with whatever you were doing." The dancing. Jack dancing with Rose. Rose dancing with Nine. Nine offering Jack a dance. Everything Ninerose related. "Before you, I was a coward." The fact that Jack only makes sure that Rose is safe before dying for them, Rose brings him back to life, Nine's every interaction with either of them in the finale...honestly the way that Ten interacts with Jack in Utopia (ESPECIALLY the scene in the radiation room/Jack's reaction to hearing Rose is alive) makes even more sense if you realize that he and Jack are exes and that they once loved each other and Rose equally and then the Tenth Doctor WRECKED that by leaving Jack behind