One of my friends from church growing up was from Nigeria, and apparently there's a culture within Nigeria that doesn't believe in naming their kids until they come of age. He had no first or middle name, just his family name. He went by Cory, which is apparently what his parents planned on naming him once he was (iirc) 13, but it wasn't "officially" his name. But apparently it caused all sorts of problems for them when they immigrated, and the US makes it much more complicated than they expected, because they were used to more informal/traditional/less legalistic systems around it.

Caveat, I was like 9, so I may be misremembering some detail. I'm also only, like, 80% it was Nigeria. I know it was Africa, but I'm not entirely positive it was Nigeria, but I think it was.