“I want to know why DNA wouldn’t sort this out?”
I don’t think the DNA tests at that time could differentiate the DNA from what appears to be brothers from different baby mommas.
I think you underestimate c2000 capability.
I’ve been gorging on “Forensic Files” which is from around that time as are many of the stories. Plenty of DNA evidence flying around, and from earlier, too. Basically after ‘90 is when DNA started taking off.
I wonder if they do not bother because “it’s ONLY robbery”, not murder.