Are your sister's children's cousins your children's cousins too?

Answer 1

Yes, the children of your cousins are also your cousins, but a different kind of cousin.

The child of your first cousin is your first cousin, once removed. The child of your second cousin is your second cousin, once removed.

The child of your first cousin, once removed, is your first cousin, twice removed.

On the other hand, your child and the child of your first cousin are second cousins to each other. Your grandchild and the grandchild of your first cousin are third cousins to each other.

Answer 2

That depends on the blood relationship. Your sister's children have cousins on their father's side if their father has siblings who have children. Those cousins of your sister's children would not be cousins to your children. On the other hand, if you and your sister have other siblings who have children, your children are all cousins.

Answer 3

Your uncle's sister is your aunt, unless she is your mother. So her children are your first cousins, unless they are you and your siblings.

Answer 4

Yes.

Your aunt's brother is your uncle and his kids are your first cousins