Khan and Kujra intercase marriage issue- afraid of brother

Hi....
I m from darbhanga,bihar...
I love the guy from 4yrs....i can't live wothout him...my sister nd mom is not ready to listen abt me in dis topic...bt i can't marry any1else....my caste is khan nd his caste is kujra....wt can i do....in dis case i have two option- one is to run away from home....which i don't want to do for sake of our parents and 2nd is commited suicide...wt can i do...???
My elder brother is don't knw abt this he love me sooo much bt he is angry young man....
How can i convince my brother...????
Plzzzzzzz suggest me....
Otherwise i don't want to live