My best friend grew up in Mexico City. She goes back for music festivals and stuff, and has shown me photos of a lot of the amazing old ruins and neat cities she's been to.
But she'll also talk about how bad the gang violence is, and how much stuff her parent's didn't let her do in the city when she was younger due to the violence. Still, she loves the country, but acknowledges how bad things are economically and from security standpoints.
Your cousin will hopefully be alright, as long as he's aware. But people do get kidnapped and held for random. It's not that common, but it's not non-existent.
My friend knows a lot of people who stay and live and raise families in those areas ... people also raise kids in Chicago. I lived in Chicago and was never shot at .. but the year after I left, a guy was shot in his car on my block. A month after I left Cincinnati, a woman was shot in front of UC Health, at the building I walked through ever day to get to work.
:blobcatshrug: