It would be so cool if this was just a case of someone regularly mistaking your aunt’s car for their own. “Huh, my key’s not working, oh well, I know a trick to get ‘er started”
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Nice elderly lady at work asks us to take out her car at lunch to diagnose a noise. We found her '73 Buick Skylark in the multi-story car-park and went to lunch. Ran great. Afterwards I asked, "I thought you were Baptist? Why did you have a St Chris statue on the dash?" Of course she didn't.
We had found the "wrong" car on a lower deck of the car-park but when we got back from lunch parked it on the uppermost deck, unaware it belonged to someone else. When we discovered our error, we imagined what the owner might go through when the car was discovered missing but we kept our mouths shut, fearing some sort of liability.
I bought that old lady's Skylark. Ran like a dang tank.
When I was learning to drive in a 1990 Ford I locked the keys in. Dad just asked a random person in the parking lot with the same car to borrow their keys. It opened the door and started the engine no problem.
His Toyota keys from a different year / model truck fit it just fine.