You can help them. There are things you can do. They're so very, very young and they deserve a Mum who's not selling or using drugs, they deserve a calm family home, somewhere they can grow up in a healthy and safe environment. You dad knows about everything going on? If so, he can help you help them. You could call social services and they would be taken to a place where they're safe. It sounds like such a difficult thing to do, and it will be, but it's for them. Just like you got yourself out of that house for you, you can get them out for their own well being. It will be difficult, but you want to make sure they're safe, don't you? They're so young and you don't want them having all those bad experiences you did, do you?
It'll be a very, very difficult thing to do. I suggest you talk to your father about it, you'll need some support. Try not to be so hard on you. It was a difficult, but brave, decision you made to leave home and live with your father. It was something that needed to be done. And now, getting your brother and sister out of that situation is something that needs to be done. You've made your life that little bit easier, and you can make it easier for Anthony and Kia.
It's not a bad thing, having to get them out of this situation. It's for them. It'll be hard, it really will, but it must have taken a lot of strength for you to have left home in the first place. With the support of your father and maybe friends around you, you can make it better for those two wee ones, it's so very clear how much you love them. You will see them again, and if you try to get them into a safer environment, you'll see them happier.
It may be two days, two weeks, two years, hell, even twenty years from now. But you will see them again.
I think it's a good idea to get away from your mother, I think you made the best choice for you, no-one need to live in a household like that if they can understand what is going on, and don't like it. Anthony and Kia cannot understand what is going on, but soon, sooner than you think, Anthony will start asking questions to his Mother. Hell, he may even find those drugs ... You need to contact government services and get those children out of that household.
They may have to go into foster care - but they can't live there. Not with the threat of drug and rape.
Please help them get out of there.
As as for you, any support you need, there is this site, there are phonelines, there are other sites. Friends, family friends.
Your father. If he is not willing to talk ... the above.
PM if you want to talk I know how much life can suck.