parents getting divorced

So I'm 16 and my parents have had issues for along time. My dad had an affair when I was born and left us for a bit I haven't been told this but I hear them arguing so I found out I never know how to react because I love my dad I get along with him so well better than my mum because me and her clash which makes me feel horrible. So basically he's cheated on my mum again and they told me and my brother I know what he's doing is wrong but at the end of the day it's there relationship boy mine so I can't hold that against him yet because I don't know the full story. The other day they were talking when I was upstairs and I heard my mum saying we need to tell then soon because they'll realise we're not wearing our rings and that he needs to move out by the end of the month all I'm asking for is if any of you girls have gone through this, I don't know how to react I feel distraught I don't know what I'm going to do without them both. I know this is best for my mum and I want her to be happy but I don't know what im going to do