If you are a recovered meth addict what would you pick as the one thing that has kept you sober?

I had 2 very very very close family members and my only brother in law start meth all within the same year and the 2 close family members stopped on their own without 3rd party help and my brother in law left rehab after 2 months but has learned alot and has stopped meth, cigarettes and even liquor i’m just wondering what we can do as a family to keep everyone sober, hope your answers help, this is the happiest we have ever been and i want it to keep it that way especially for the kids!!