hi,

see it would be no obstacles for you to appear in jee exam this year. it did not matter and would not effect on your candidature that you want to give full effort and give your best on next year of jee main exam. A candidate may appear in jee main exam to three consecutive year starting from the year of passing of 12th exam. however since your brother has filled your form just attempt the exam and it would get you some experience and you would become familiar with the process while attending  in next year.