My father used to work with someone who was originally from some Pacific Island country (forget which, might have been Fiji). And the story was, in that country

My father used to work with someone who was originally from some Pacific Island country (forget which, might have been Fiji). And the story was, in that country, at least back then, you didn't get a birth certificate at birth; to register your children with the government, you had travel to a government office that was like a day's walk away (most people didn't have cars). And so a lot of parents didn't bother doing it with their eldest child, they'd wait until they'd had a few, and then go register them in a batch. And the government officials had no proof of when the child was actually born, so they just put down the date you registered them as the date of birth. Which meant this guy had the same date of birth as all his younger siblings, despite being several years older than them. And then he used that to get a passport, and then a visa to immigrate to Australia, and then after a few years Australian citizenship... and now all his legal documents say he's a few years younger than he actually is. And he decided he wasn't even going to try to fix it, the morass of bureaucracy involved wasn't worth it.