Should I tell my parents?

So my sister & her BF who are 23 love at my parents house. They've lived therefor a year & are supposed to pay $100 a month. But they don't all they do is spend their money on drugs and alcohol. Well, I recently found out they've been letting my little brother who is 14 & who has severe asthma smoke and drink with them. At first I didn't wanna say anything cause every kid wants to have fun. But he's 14urs old and shouldn't be doing thy stuff. Also, my sister shouldn't be condoning to it because that's disrespectful to my parents. So, should I tell my parents what's going on? PLEASE GIVE ADVICE DONT JUST READ AND NOT RESPOND