If it is a boy then it is your nephew. If it is a girl then it is your niece.
a cow
Some would call your nephew's children your grand nephews and grand nieces, others would call then your great nephews and great nieces.
Your children and your grandniece first cousins, once removed, but in conversation they would call each other by their first names.
yes
Your child would call your sister her aunt.Your sister would call your child her niece or nephew depending on gender.Your sister's children would call your child their cousin.
grace adn luoi
let the children call the teacher by there first name
Your brother's children would be your nieces and nephews. Your nephew's children would be great-nieces and great-nephews.
That would be a school crossing guard.
Say if your mum wants to call you what would she say?
A paediatrician is a doctor that helps children.
Your brother's children would be called your nieces or nephews.