I think most of what you are talking about here is your parents being incompetent people. Even if they hadn't had kids, they still would have been in financial trouble their entire lives.

I don't even think this is due to a lack of financial education on their part. Feels more like compulsive spending, something a therapist might have been able to help them through had they been willing to talk to one.

Either way, it really sucks that you and your brother had to suffer so much for their failures.