My advice: explain how you feel
Parents have the biggest impact on individuals lives, especially for teenagers.
You look up to your parents and their relationship is something that you will never expect to end. Circumstances change and it's horrible but it isn't permanent, I promise things do get better.
It's going to be hard, of course it is, it will feel like your whole world has turned upside, you'll be surrounded by friends that have their 'perfect' families, good strong family units but sadly not everyone has that privilege.
One bit of advice I can give anyone is to sit down as a family. It's hard and really upsetting but it helps once you get through it. Stay out of the arguments (which I know I found the hardest), don't take sides and just explain how you are feeling.
Your parents will be worrying about you and how you are feeling about the whole situation more than they worry about themselves so just open up, let them in and don't bottle it all up, you'll feel better.
Don't feel like anyone is judging you or your family because all people want to do is help. There are people and support lines you can contact, ordinary teens just like me that will always be a shoulder to cry on.
Stay positive, you'll get through.