Aw... hang in there! *hug*
It is never easy when parents are having problems. Even as an adult child of theirs it is hard to watch.
My spouse and his siblings are adult children of divorce. While they don't need the parents like child children do -- a divorce still is felt and trickles across all family interactions -- weddings, bdays, grandkid things, etc. All the relationship dynamics change. It's like polymath only you'd call it familymath. The concept is still the same. The network of relationships takes dings on many tiers. Not just the breaking up couple link.
You will grieve. Try to do the self care you need to do for yourself and maintain your separate parent relationships how you need to be.
Will keep you in thoughts and prayers.