Well it may be that Kabir never really existed as claimed by the general belief.

I read this about Kabir and the movement some time ago, here is the relevant quote.

Kabir in History

"..There is reason to question the accuracy of some of the dates (Dates may have been transferred from History of one man to that of another bearing the same name,or dificulty may have been experienced in deciphering dates written in Persian figures, without an accompanying verbal explanation) and reason to believe that some of Kabir's biographers, working on the asumption that there was only one Kabir, have unhesitatingly appropriated details from the lives of several".
From p 14 of "Kabir and the Kabir Panth " ISBN 81-215-0000-1.
The book then carries on naming several Kabir's that existed in that time.

Take care