First of all you should ask your parents to explain to your brother that although he does not follow halacha, the atmosphere that they want to retain in the house especially for the rest of their children is one that does follow halacha. Therefore its only right that if he needs to watch movies he should use headphones so that everyone else not be disturbed.
Secondly, going off the derech is not always controllable. Sometimes parents do everything under the sun to teach their children the right way, but the child’s nisayon is between him and Hashem. Your parents shouldn’t feel guilty, they should only do their utmost to express to your brother how much they love him no matter what he’s doing as often as possible. Don’t try now to be mekarev him to yiddishkeit, be mekarev him to your heart.
If you are scared that you’ll go off, reinforce a love of yiddishkeit in yourself. Read and learn books that speak about Emunah and Bitachon. Learn Chumash with Rashi every day. Find a Rebbetzin (I’m assuming you’re a girl since your name is riki77) that you look up to and make a strong kesher with her.
You too should only show your brother love and devotion whenever you can. Be strong and firm if he tries to convince you to do things you wouldn’t do but never through arguing. Everything should be with love.
I have a chavrusa who told me of a boy on his block who went off the derech but his father worked hard to maintain a strong loving relationship. The son tried to keep everything hidden from his father and one day someone caught him watching TV on Shabbos. The boy was so scared that it would get back to his father because he didn’t want to upset him. Within a year he was back in the Beis Midrash. This shows you the power that love has.
Be strong, daven for him from the depths of your heart and show him how much you care for him and have faith that Hashem will help him.