“He” or “she”, “his” or “her” for an ambiguous name

Question

In Finland Kari is boy's name and in Norway it is girl's name. Suppose I meet a Norwegian Kari. Which one is correct?

First I heard his/her name I thought he/she is a boy but the I realized he/she is a girl.

Answer 1

Well, you do know that she's a girl now. You are talking about her and not some sexless blob. So the sentence should read,

When I first heard her name I thought she was a boy, but then I realized she is a girl.

Answer 2

The only important thing is, what the person's sex is. Thus:

First I heard her name I thought she is a boy but then I realized she is a girl.

Note: Some names are even in one and the same country used for both sex. What would you do in that case, if you depend he and she on the name?!

Answer 3

In common English, one can use their/they to signify unknown gender.

Kari went to my friend's house for dinner; they brought a bottle of wine.

So, in your case:

When I first heard their name I thought they were a boy, but then I realized she is a girl.

This keeps the ambiguity until the end, where it's clear you're talking about a lady, rather than a man.