Its the same old story with Kenyans and their birth dates being registered late.
I would guess he was 16 (at a stretch 15), when he ran that time. A 12 year old just does not have the strength to run a 1:49.
There have been a number of 14 year olds who have run around what Kevin Sullivan ran, but to run 4 seconds faster and be two years younger is just not realistic.