It is always sad to when I get a question from some one other than a user his/herself. You, by yourself can not do anything without him wanting to do it. You can haul his behind to an NA meeting, you can get him into rehab, you can even get him to my clinic and I will get him physically clean, but without his commitment and his desire to stay clean, all of it is useless. Suboxone is just another opiate, it does work for some, but again, a person needs to want to quit. Your brother does not. My heart aches for you, because you are truly helpless in this situation, and he is in control of his own deadly destiny. It will lead to nowhere good and it is awful to watch.
Young, smart, talented people die of overdose all the time and their loving families can only watch their disintegration while shedding tears.
Tell him you can not house him while he is using. Most likely your uncle gave him the job as a lust ditch effort to help him, but it will not last if he is using. He will have to come to a place that is very dark and scary and low to realize that he needs help. If he survives that place, there are options. Read my blogs by clicking on my name and then blogs and read some of them especially about detox options and others if have time. Good luck to both of you. You will be in my thoughts.