I can't offer any personal experience, but I think another important question to ask would be, what is the reason for the split up.
If your mom splits with your dad because he is abusive or has a dangerous addiction, this is much different from some other reasons.
If you have an idea as to why they split this might make resentment very understandable, some other minor reasons might make resentment unreasonable.
"Anarchism is not a romantic fable but the hardheaded realization, based on five thousand years of experience, that we cannot entrust the management of our lives to kings, priests, politicians, generals, and county commissioners."