Controlling Multiple Assassins in Assassin's Creed: What's Possible?

Depends on "control":

• Simultaneous dual control (single player): Impossible in all main games. You control one protagonist.
• Different protagonists across series: Yes. Altaïr (AC1), Ezio (AC2/B/R), Connor (AC3), Edward (AC4), Shay (Rogue), Arno (Unity), Jacob/Evie (Syndicate – switch at will in open world), Bayek/Aya (Origins – Aya playable in few missions), Kassandra/Alexios (Odyssey – pick one), Eivor (Valhalla – male/female/animus switch), Basim (Mirage).
• Co-op (Two Players):
  • Unity: 2–4 player co-op missions (custom Arno).
  • Odyssey: "Story Creator Mode" / limited co-op? No, Odyssey is SP. Valhalla: No co-op.
  • Assassin's Creed Nexus (VR): Single player.
• Recruit / Brotherhood System (SP): Brotherhood / Revelations / AC3 / AC4 / Rogue: Call AI Assassin recruits (Arrow Storm, Guild Challenges). You command, don't control directly.
• Switching Characters Mid-Mission: Only Syndicate (Jacob/Evie) in open world (hold D-pad). Missions lock to one.

True dual-control co-op: Unity (only mainline). Otherwise, sequential protagonists or AI recruits.