<human>: Summarize the given text in a few sentences.

Hi there, and thanks for reading this.

In August, my father died. My sister and aunt read the will and found that the entirety of my father's liquid assets was intended to be given to cancer charities.

We all thought that his estate had been formalized.

It wasn't. In December of 2014 my uncle walked in with a death certificate and a notarized statement claiming he was the successor of the decedent. I found this out at the bank today when I walked in with a death certificate.

The reason I went is because my aunt called me asking me why I told my uncle I didn't want anything - which I hadn't. He's a jerk.

So he made off with ~$40,000US.

So my questions are focused on what my options might be.
Can a challenge his claim of successorship?
We have a "will" in my father's writing regarding his intentions. In it, he claims he has no living relatives - which is sad, but considering we've all pretty much left each other alone for over a decade is not surprising.

Sure, I'd like to have some of these funds to pay down student loan debt; Lord knows my father didn't pay any alimony when he divorced my mom.

But if the end obligation is to give this money to the ACS or a similar organization, I would like to ensure that happens.
<bot>: Uncle "stole" deceased father's money that should have gone to cancer research. How can I work with the law to make it right?