Before the island
When they were young, Eko was protective of Yemi, even stealing food because Yemi was hungry. They used to play soccer together. One day, militant thugs came to Eko's childhood village home to kidnap children to join their ranks. An unidentified Nigerian guerrilla member tried to force Yemi to shoot an unarmed man. When Yemi refused to fire, Eko grabbed the gun quickly and shot the man without hesitation. As a result, Eko was recruited into the guerrilla group instead. Eko's cross, which was thrown on the ground by the Thug captain, was picked up by Yemi, who held onto it in anticipation of his brother's return. ("The 23rd Psalm")
Yemi moments before his death. ("The 23rd Psalm")
Years later, Eko became a warlord and returned to the village with the intention of taking advantage of his brother to further a planned drug smuggling operation. Eko coerced Yemi into signing documents that falsely confirmed Eko and his cohorts to be priests. Yemi reminded Eko that this would not really make him a priest. He accepted the drug money offered him by Eko in return for signing the papers. Yemi then informed the Nigerian Army about Eko's gang's shipment of drugs, and was shot trying to save Eko from being shot. He was then loaded into the drug smugglers' plane while Eko was left behind. ("The 23rd Psalm")
On the Island
The plane carrying Yemi crashed on the island in 2001. The crash was witnessed by a time traveling John Locke. Locke attempted to discover if there were any survivors but before he could he was shot in the leg by Ethan and continued moving through time. It is unknown whether Yemi was alive at this time or if he had already died from his gunshot wound. ("Because You Left")
As a corpse
Eko's cross on Yemi's corpse. ("The 23rd Psalm")
After the crash of the plane (which Locke saw in his vision), Yemi, and Goldie (one of the Nigerian drug smugglers that worked with Eko) died. Yemi's corpse was found on the island when the Drug smugglers' plane was discovered by Boone and Locke. Eko found the plane later on, recognized his brother and took his cross back. Eko burned the plane on a pyre, saying the Psalm 23. His body goes missing sometime between "The 23rd Psalm" and "The Cost of Living".
In Eko's visions
The Man in Black appears to Eko as Yemi, right before he is attacked by the Man in Black in his Monster form. ("The Cost of Living") (promotional still)
Yemi (actually the Man in Black) appears in Eko's dream, and tells him he needs to find the "?" with Locke. He later appears in Locke's dream to guide them to the top of the cliff, where they can see the question mark.
Seven days later, the Man in Black appeared to Eko as Yemi once more, telling him that it was time to confess. Locke's hut catches fire, leaving Eko inside, but he is rescued by Charlie, Hurley and Sayid. Eko went back to the plane and moved rocks only to discover that Yemi's body was gone. Feeling discouraged and helpless, Eko encounters Yemi again. Yemi, now with dirty clothes, told Eko once more that it was time to confess. Eko followed him to an anemone field, and said that he feels no guilt for what he did, and that he would not confess. Yemi said "You speak to me as if I were your brother", and left. Moments later, the Monster attacked Eko, and killed him. ("The Cost of Living")
- Yemi is a Yoruba word from Nigeria which means 'By virtue of self I am worthy of it'
- Yemi's situation bears similarity to those of Christian Shephard and John Locke, as they both died off the Island though when their bodies later crashed on the Island they appeared in visions.
- It was confirmed that Yemi is a manifestation of the Monster on the island. (March 21st, 2008 podcast)
- For fan theories about these unanswered questions, see: Yemi/Theories
- What happened to his body?