Anyone worried their sibling will become a NEET?

I'm in the same boat. Slightly worse actually. No solution here - just offering mental and emotional support

insightful, thanks for this

Let's compare notes with you and my sibling.  Mine has been doing this nonsense for three years now since he graduated, or for longer if you count making zero plans for post graduation while in school

• Mine is also a fairly smart STEM kid, but did not go to as prestigious of a school
• Worse career than your sibling - how the fuck did he get his first job anyways?  Mine is just a permanent semi-student, "deciding" on what he wants to do
• Zero interest in any kind of jobs

At some point, you need to accept that you cannot change how people are.

He has had many, many chances to start digging himself out of this pit but doesn't because he thinks it's cringe, or looks down on people who have jobs they don't enjoy, because he is afraid of failure, because he's spoiled, or whatever.

My parents who still treat him like a college freshman have also had many chances, but instead they choose to live out their golden years taking care of a spoiled man child.  They haven't taken a vacation in years, but once again, their choice to treat him like he's infallable.

You personally risked your reputation with your friends by vouching for someone who has zero social skills and most likely would be a terrible coworker.  You have also offered him money for therapy.  You have done more than enough.  If he reaches out, help him, but you have your own life to worry about.

PS: 

1. How are your parents reacting?  Mine used to have some sense, but now I can't talk to them about it either.  They think he's "improving" now.
2. What is your sibling doing all day?  Do you know?