My Brother had filed petition for me under brother and sister relation in F4 category. The priority date is October 12, 2007. The petition is approved and received by NVC on March 7, 2008. My brother filed for my Parents as well and they are citizen now. Please suggest, if, my parents can replace my brother as a petitioner and change the status of file to F3 category? and what will be the date of priority, if possible. Kindly advice which form needs to be submitted if this is possible.