The realty is owned as tenants in common by husband and wife. When the first spouse died no estate tax was filed and the will was not probated.When

There is no estate tax between husband and wife so no estate tax return would have to be filed.  I'm not sure why you are concerned about who gets what share if both spouses are dead.  Were the wills of each person different?  Is the disposition different?  Or is the concern did the whole house pass to the surviving spouse, and then the surviving spouse's will governs what happens to the house?  If you have more information, please feel free to call.