I read from another person in this forum that it could be better to apply for your parent's GC only (can this be done??) and wait 5 years till they become citizens and then, they can apply for your sibbling. This would be good idea if your sibbling would still be under 21 at the time your parents become citizens. That way sibbling only waits 5 years. Otherwise, Dr Lha is right sibling would have to wait....around 10+ years for GC.....check with a lawyer....