This isn't about emotion. It's about what the courts will and won't consider, you know? You know as well as everyone else on this thread - no, the entire board - that nobody is even vaguely suggesting that you should not care, or appear not to care, about the boys. You're letting emotion overtake the legal reality there.
But this isn't your fight. If Dad wants things to change - DAD has to make the moves. If you see abuse, and the kids' Dad sees abuse, you report that abuse.
Because come on, when all is said and done - the responses you've seen here today are nothing compared to what a judge would say if you presented this thread to him verbally, the way you have here today. If this has gotten to be too emotional today, take a step back and read the forum for a while. Read the old threads. Go back a year or two, even. You're going to see a pattern of "coulda shoulda woulda", and you're in a position now where you can either hurt Dad's chances, or help him. Pick the right one.
Let Dad take care of things. Research for him by all means...but if you really, truly want to support him and his kids, then you DO need to step back and let the kids parents sort this out.