Difference between family name, name at birth and first names?

I'm filling an English document and I'm being asked to complete my family name, then my name at birth and then my first names. Does anyone know the difference between these 3 concepts? My guess is that my family name is my last name, my name at birth is my complete name at birth, and my first names are everything but my surname. Is that correct?

Answer

Here's the common usage of those terms but for a specific form check with whoever is asking for the form to be filled out.

Family name is the part of the name you share with your family, often called "last name" or "surname" in English (though that's less accurate since some cultures put the family name first).

Name at birth would be your full-name on your birth certificate (usually the same unless you've changed your name).

First Name is your given name (strange to see a form that mixes "first name" and "family name") if it says first names (plural) it might include all other names other than your family name (eg middle names).