Twin theory refuted by facts L, I, and E: empty tomb implies no second body; intimate companions would have known; family members converted

If a twin died in Jesus's place there would be two bodies, not an empty tomb. The post-resurrection appearances were to people who had lived with Jesus daily for years and to his own family members (including his mother and James his brother) — they would have recognized an impostor. James's conversion specifically is hard to explain if the appearance was from an unknown twin.