Family issues. PLEASE help...?

So my aunt and uncle have had a horrible year so far. They have 2 kids. One (girl) is 15, and the boy is 18. Well my cousin, the girl, was diagnosed with melanoma. That shook up the entire family. That's not the worst part. The 18 year old has put the family thru hell. He stole his dad car and spent $3000 without permissin, moved out to a place 12 hours away and got involved with drugs. He came back, and my aunt and uncle made the mistake of leaving him home alone for the weekend. Turned out he threw a party, and about $2000 of goods (laptop, jewelry, etc) was stolen, windows were broken and it was a mess. Now he got caught with some weed, and blamed my cousin (he's 20) for using it ( which is ABSOLUTLEY not true.) so my 2 uncles are very mad at eachother. The father of the trouble maker is afraid to dicipline him, because they don't want him getting involved with drugs and crime again. What can we do? He's tearing our family apart, and my uncle won't dicipline him. Help?