GTA 6 has two leads, Jason and Lucia, and An Extended Look showed the player switching between them, including mid-combat. Lucia is the first female co-lead in the modern 3D and HD-era Grand Theft Auto series.
What do you want from the pair? A heist-movie rhythm, a slow-burn partnership, a long game of who is using whom, or something we have not thought of? And which of the two are you most curious to play as?
Keep to what Rockstar has actually shown or said, and mark anything else as your own guess. Our characters page lists what is confirmed.