Just found out my brothers are doing drugs?

my two brothers, both of age, have been smoking weed since they were 12. i know they've abused different drugs in the past, and both have been in prison for minor drug charges (possession of marijuana, paraphernalia, etc..) I've recently found out that they are both back into drugs, heavy. Now their snorting Roxie's, which is basically synthetic heroin from what I've been told. One brother drinks heavy, and the other has joint custody of his 4 year old daughter. He stays clean when he has her, but cannot keep her for more than a day before he gets "dope sick", and calls the mom to come get her. My question is, is there anything I can do or say that will make a difference. the rest of my family has no idea, but I know my parents would freak if they knew. My parents might be able to get through to them if I can't. Should I tell my parents that my siblings ar eon drugs, even though they'r e over 18?