My deepest condolences. It's crazy that your uncle and aunt are acting that way and to me shows just how much this religion can amplify someone's naturally bad tendencies. Interestingly enough, they act the exact way that they claim those "in the world" act. I'm especially thinking of 2 Tim 3 where it says that in the "last days" folks would act poorly and one of the things listed was "no natural affection" (vs 3).
How can they justify treating anyone that badly when their own religion (on paper at least) tells them to comfort those grieving? There's even an exception (can't remember where - don't have the WTL at work) that allows JWs to drop the shunning at furnerals to comfort the mourning. It's just insane. They're so self righteous they won't even follow the instructions "mother" has provided. These two are a piece of work.
I'm so sorry they made a bad situation worse. They sound like the type of people that you're better off not having in your life anyway.