The only family member we've heard from is the uncle who I believe quickly pointed fingers at the ex. I wouldn't be surprised if other family members might do the same. LE may not want that if they have suspicions when it comes to the ex. Especially if there is some huge piece of information that paints ex in a very negative light.
From what I saw, it seemed as though it was the ex's family/friends who weren't aware of the divorce, but is the same true for Crystal's family? If she was the one who filed for divorce both times, it would be reasonable to assume she was the one that was unhappy. She may have been complaining about the ex to family/friends for the last 10 years. It would stand to reason there were some red flag behaviors brought up over 10 years. I cannot imagine an unhappy marriage not having a few. But those are the things that stand out and are easily remembered.
There's also a possibility that family knows way more than the BF and they don't want any important information being leaked.