My aunt and uncle had their twins' names picked out (boy/girl) before they were born. But the little girl had to be whisked away to a different hospital for surgery (she was born missing a valve in her heart), so she had to be baptised immediately. My aunt wasn't even present, and my uncle gave her a different first name than the one they'd decided on. My other aunt (both my mother's sisters) was PISSED, because he gave his daughter a name she'd planned on using for HER daughter, and we have an unspoken "no doubling up" rule.