They were born in different years. Their SSNs were not close. For one of them the name was her maiden name. For the other, a married name. They went to different colleges and had different credentials. They did live in the same town.
When my aunt died, all the credit companies and collections companies tried one of two recovery tactics. Some tried to make her brother pay the debts as her surviving spouse. The others tried to assert that the debts were incurred by his wife and that the mismatch of other data in their own databases was evidence of fraud.
I'll bet that pair has stories to tell.
We always double-check dosages for medications before taking them.
Every time one of them goes to a particular medical facility, he has to explicitly decline having them merge their charts.