Innocent.... family visas dont need an NOC. Your sister cannot sponsor you to come on a 6 month visa. She is here under her husband sponsorship and she cannot sponsor anyone, he would have to do it and as he is not your direct relative he cant do it.

Catch, if he had no RP he doesnt need an NOC. How is he still here in the first place? If he is under a business visa from the previous employer no other visa can be issued for him.

"Diplomacy is the art of saying 'Nice doggie' until you can find a rock - Will Rogers"