Sorry to hear about your situation In the house.
I would suggest you take the following measures:
1- Have you tried talking to them about the issue?! Are they approachable in that sense?!, if they are, I would really suggest sit with one parent at a time and put your concern forward (In a very respectful and calm tone). It could be done with all four siblings with a parent or individual child with a parent at a time. At times there is a child who can approach either or both of the parents easier than the other, that way the message will be sent across and they could then rethink regarding their living style.
2- If the above is not do-able speak to an elderly, who your parents will listen to. Say a grandparent from both sides?! If that can't happen, maybe a family friend or local Aalim that can send across your unhappiness to your parents. That way they will definitely try to resolve thier approach with one another.
3- Please look into duas that you can make for them. Speak to Allah plentiful regarding your concern and I'd also suggest seeing Sahifah al-Sajjadiyah and recite the dua that best describes your worries.
4- Constantly recite ayah no 69 from Sura al-Anbiyah in thier presence. It really helps you and them to calm down.
I hope this is resolved and your are able to enjoy them