Unexpected letter saying I am the beneficiary of a life insurance policy

My dad passed away in early 2017. I was his only child and he divorced my mom when I was a baby, never remarried, had no close family or friends really that I knew of. I was not aware that he had a life insurance policy either, but today I got a letter from American General Life Insurance saying that they believe he might be deceased and that he had a life insurance policy that would need to be paid out if so. It had a few papers I had to fill out including my name, ssn, address and a certified death certificate to verify that my dad has indeed passed. So I filled it all out and mailed it off.

Now my concern is that I am unsure how legit this all is and if there is anything that could happen from the information I sent out. I called the number that was on the letter and spoke to them until I felt comfortable, then I googled the customer service number for the life insurance company and called that number as well to make sure I was talking to who I assumed I was. When I called the AIG customer service line they too the claim number I had and my dads SSN and with that were able to verify that he has a policy but I was not the beneficiary, and whoever was, they attempted to contact, but they are apparently deceased as well (both numbers I called said this same thing) and that the money would go to the next of kin if my dad had no estate, which he did not. I am the next of kin, therefore would receive the money once I verify my identity and my dads death.

Does that sound legit or scam likely? It is all I can think about at the moment and I need to get focused on school so I am hoping to hear of a similar experience or something I suppose.

Thanks!