Missouri  |  Wills and Trusts

Proof that I am next of kin to deceased?

After my moms death, the auto insurance company issued a total loss check in my moms name and her ex's name. His bank will not cash it because it has her name on it. Even with a death certificate, they wont. What do I need to get to prove to the bank that I am her daughter, (she wasnt married) and to get them to cash the check? Powerof estate??? If so, how do I do that? Who do I contact? She had no will, but I am the benificiary on the life ins. policies.