Reddit, I feel as though my younger brother is growing to be a disrespectful, ungrateful punk. What can I do, as a brother, to help this not happen?

My parents aren't home for more than 2 hours during the weekdays, and there's pretty much no one else who has any kind of influence on my younger brother. He's not grateful for anything he has. He acts as though he's entitled to things he doesn't even own. He's completely dependant on the rest of the family for everything. Also, probably worst of all, he lacks respect. He will disregard what you tell him, and treat your property as if it's his and he owns everything he touches. He seems to be on this high horse he won't get off of. My parents are oblivious to this because he becomes a perfect angel in their presence and although he doesn't do well academically or with his responsibilities in the house, my parents are too weak-hearted to punish him.

Now, I'd typically say he doesn't know any better, but he does. He just refuses to care about the things or people that run his life. So reddit, I ask you, what can I do that could have a profound enough effect on him to change his ways? I really feel as though he has the potential to have such a better character than he has now and it pains me to see him be so inconsiderate.