Rick, no offense taken, some jokes were made at the time.
Long story short: cousin who was born and raised in Houston died in an accident in 1992. Young, unmarried, no social security death claim was made, so SSA didn't know he had died.
In 2004 an uncle found that my dead cousin was now listed in the Houston phone book! Very Germanic name, he was named after my great-grandfather. Uncle called, and got a man with a heavy Spanish accent who could barely speak English. We investigated, found he was using my cousin's SSN and birthdate.
I went to a DPS investigator who got the ball rolling. When they confronted the guy, they had my real cousin's high school yearbook with the names covered. Of course he couldn't identify any of his classmates, and he confessed after they pointed out that one of the ones he couldn't identify was actually a pic of my cousin.
Yes, he was an illegal alien. And he got away with this for about 7 years! He slipped up when he bought a house and forgot to tell the phone company he wanted an unlisted number. D'oh!