Send them back.

Are you sure they're not survivor benefits?

No, she's still getting two checks: one in her name and one in her husband's name.  

Was she getting checks before her husband died?  I'm not sure you have a tax question.  

I was hoping for an opinion about whether I should claim his income on her taxes.

If he is deceased, how is he getting to the bank to cash them?  Hopefully she isn't forging his name on the checks and cashing them.

direct deposit

Since she is keeping it, it's taxable.  It wouldn't even qualify for the special treatment for Canadian Social Security (0%-85% taxable depending on amount of other income) because basically it's just stolen funds.  If she ends up paying it back she has a "claim of right" computation in the year it's done.  Canada has an embassy and 13 consulates in the U.S. -- I wonder how hard she is trying to resolve the problem.  And can't she tell her bank not to accept them?

She's 90 and doing the best she can.  She escaped the Iron Curtain around Hungary, was accepted in Canada, and then the US.  She's called three times and written once and is still hopeful she can get it resolved before 2022 tax season.  "Stolen" seems a bit harsh for an elderly widow trying her best.

Thanks for the opinion about claiming it and pursuing the claim of right.