芈兰 / Mi Lan
芈兰 / Mi Lan appears in 《资治通鉴·周纪》62丨稷儿，诓你舅舅的“腿”啊 as a son of 楚怀王 who supports attending 秦昭襄王’s proposed meeting at 武关. The source says he has married a Qin princess and treats that marriage tie, together with the kinship through 芈八子 / 宣太后, as reason to trust Qin enough to go.
His role is source-scoped but structurally important. Mi Lan’s advice turns 战国联姻外交 from an alliance signal into a false comfort: family connection makes the trap seem less likely, even though 秦国 closes Wuguan and detains Chu Huaiwang in 咸阳.