I am sorry for your loss and the mess you are in.
If the condo is really "tenants in common" and not "joint tenancy" then you and your brother are entitled to dad's 1/2 of the condo.
Depending on the value of his assets (more or less than $150k) will determine what level of probate is needed.
The New York Department of Finance (I think dfs.ny.gov) has a life insurance search form. That's free. Or you can pay $75 to mib.com for a search.
If you are confident there is no will then I wouldn't worry about what your brother says.
Go hire a probate attorney, today, and get this started.