I lost my pword to my yahoo account i did not make it my brother did so i dont know what info he put in it?

can some one help me i did not make the account my brother did and I do not have any of the info that he put on it. Ive tried puting info in that i think he may have put in it but its still not working ......he must have put the wrong birthday and postal code and i don't know what to do ...i dont have any information please help me1!!!!1