Maybe. They are only related if they share a common ancestor. There are lots of possibilities and some of them will be related and some will not.
Your daughters are great aunties if their nieces have kids. Your daughters kids are your grand children.
Cousins
They are your nieces and nephews and not your cousins
Your mother's sister's children are your 1st cousins.
Children of your siblings are nieces and nephews. Children of your spouse's siblings are still called nieces and nephews, but you are not related to them by blood.
Auntie is a loving term used by some instead of aunt. Aunties are aunts to their nieces and nephews. An aunt is the sister of a child's mother or father.
Your mother's nieces' children are your mother's grand nephews or grand nieces. They are your first cousins, once removed.
Second cousins.
Your borther-in-law's children are your nieces and nephews. You are their uncle or aunt, as is your spouse.
You don't, simple as that. You could say cousins if it's that important, or "my aunt's nieces and nephews on the other side," but there isn't an actual term for that except your "uncle's wife's siblings children."
Your father's great nephew is the son of your father's niece or nephew. Your father's nieces and nephews are your first cousins. Their children are your father's great nieces and great nephews, and are your first cousins, once removed.
Your aunt's children are your first cousins and theirchildren are your first cousins, once removed.Your children and the children of your first cousins are second cousins to each other.