Is this illegal, what they did?

Basically one of my uncles died, and his cousin and the cousin's wife had access to the house, and after he died, they basically went through everything. He kept all of his money in the house, and he had maybe 150,000. He in turn relied on his aunt to pay for everything,so he never wasted any of his money. That cousin, and his wife may have found that money, because so far they were living frugally, and all of a sudden they're buying new cars, houses, condominiums..etc. Is it illegal what they did? The uncle had a daughter, who's basically living in poverty, so I don't know if she was supposed to get that money as his only heir so to speak? Thanks for any answers...