I need advice on an investment account

So I 20M, have started a sales job and I’m making more money than I ever have, now the bar is set pretty low since I haven’t worked too many jobs. But full disclosure, I’m currently on track to hit somewhere between 80-90k a year if my sales stay on this pace. My expenses is pretty low as I live at home for now, the only thing I pay for is my car and insurance then my family’s phone bill. My situation is I’m currently investing 8% of my checks into a 401K but I need to do something for my brother. My brother 17M turns 18 soon, is special needs. He has autism and a few other issues he deals with on the daily. My family recently found out he basically won’t be able to work a full time job or even live on his own. (We kinda knew but it’s definitive now). It’s come to my attention that my parents have not setup any type of fund for him, and also their retirement fund is not huge either. Since they clearly have their own issues, what are some ideas I should do my own self research into for this fund?