Dad's SS income is less than mom's. If he were to pass away before my mom, will she get some of his SSI in addition to her current SSI?

Thanks to all of you for your responses. It helps to have a general sense of what to expect. :-) I'll check with the local SS office too.

When a Spouse dies the surviving spouse receives the higher of the two SS payments. The lower drops off. So Mom, having the higher, gets hers and Dads drops off. She will need to go to the SS office just to make sure she is receiving what she should.

If it had been the other way around, Dad would have gotten the increase.

Stepdad passed first, on their tenth anniversary. He believed that mom's SS would increase if they had been married for more than ten years. Mom's SS did not increase, her benefits were lower than his, her income was too high from SS, 401k, etc.

No change in the amount.

She will receive what she is already getting, nothing in addition, unless she is under the poverty level, then some additional assistance can be gotten from SS.

I believe your mother will continue to receive the same amount as she had been receiving prior. No change as she was the higher earner. Her SS will not be augmented and the only change will be cost of living increases determined by the government & economy.