Welcome to the forums. I’m glad that you decided to reach out here because it sounds like you’re having a really tough time. I can hear how stressful this situation is for you and, I’m sure, your whole family. I really feel for you all.
Firstly I’m worried about you. Unfortunately there might not be a lot you can do at the moment to help your parents get through this. I’m sure that they both know that you love them and that you want what’s best for them. I know it’s hard, but they’ll need to work out how to deal with this together. I think that it’s most important at the moment that you and your sister have some support to get through this hard time.
Do you have anyone in your life that you can talk about what’s happening? I wonder if you’d be willing to see your school counsellor or a psychologist. They’ll be able to give you support by you just being able to talk about your worries, and also give you some skills that you can practice to cope with the feelings that are coming up. If you go to your GP you can ask for a Mental Health Care Plan so that you can see a psychologist 10 times per year for free. If that feels too hard at the moment, is there another adult you feel comfortable with that you could talk to, like a teacher or other relative? I don’t want you to be alone in this.
There are also some services online that you can get in touch with. The best is probably Kids Helpline, which is for people up to the age of 25. They have a 24 hour phone line on 1800 55 1800 and also 24 hour online chat through their website. I think it would be a great idea to speak to them because they would have a lot of resources for your type of family situation. You mentioned your sister, maybe you could suggest it to her too?
It sounds like your mum also needs some support. Would you ask her if she’d think about talking to someone? It must be very hard to see her struggling and so upset. You’re being very brave through this, but I don’t want you to take on too much responsibility. You can mention to your mum that she can also get a Mental Health Care Plan, or else she can contact 1800RESPECT (they have a website) because they’ll be able to tell her about a whole range of services that might be able to help her.
I’m so sorry that you’re going through all of this. Please take care of yourself and keep reaching out for help when you need it. You’re being really strong, but I want you to have someone you can lean on too.