Just to carry on the religion theme. In the garden, after Eko wouldn't confess, Yemi denied knowing him "You talk to me like I'm your brother" Like one of Jesus' disciples denied him before he was crucified. Of course this was after the whole resurrection scene so it probably wasn't.
On the other hand the quote may just mean that EKo was hallucinating and was really talking to someone else (the others, smokey)
I took it to mean that Yemi was NOT his brother. Smoky took the form of Yemi (Which it had seen in the plane and from Eko's memories) and tricked Eko into trusting it.