You call a person born in Ireland, Irish.
You would call this person a child. By the time a child reaches puberty, he or she knows.
You can call your child whatever you want I mean it's yours.
A firstborn child is the first one born to a couple or individual; normally the eldest child.
Mature
Human
A person under a legal guardianship is called a Ward.
A parent/guardian
German
pedomihner
An Anglesubriacht
Scottish :)