What do i call my great uncle's children?

Answer 1

If the children of your great uncle's wife are also your great uncle's children, then they are your parent's first cousins, and your first cousins, once removed.

If your great uncle's wife has children from a previous marriage, they are not related to you because you have no common ancestor. However, if they were very young when their mother married your great uncle, it may be convenient to treat them like "members of the family" and call them your first cousins, once removed.

Answer 2

Your great aunt's children are first cousins to your parents. They are your first cousins, once removed.

Answer 3

your cousin.

Answer 4

They would be your third cousins.

Answer 5

Your uncle/aunt.