US embassy claims my brother petitioned for me to get a greencard but he doesn't remember doing so ?

how can this be possible…are there not certain documents he has to present to file a petition.. also if the us embassy insists that he filed a petition and they have this on record for 6 years.. does this mean they had approved it and therfore i have a case number buy my brother is not aware of it ?,,,
By the way my brother has been a legal resident for about 10 years and a US citizen for about 5 years…