His great uncle
Your uncle's son is your first cousin.
great uncle
Your uncle's son is your first cousin.
It means you have (or had) at least two uncles and at least two great-uncles, and that is all it means.
Your brother's daughter's daughter is your great niece.
your uncles son is your cousin
They are your Uncles and or Aunts.
It could be your son. It could be your nephew as well. It could be no relationship to you at all. The question is do you share a common ancestor? If you do not have a common ancestor, you are not related.
First answer:that would be your second cousin. It is legal in the united states to marry them due to genetics Second answer:Your question is: "What is the relationship of your uncles son daughter to you?" If you are asking, "What is the relationship of your uncle's son and daughter to you?" they are your first cousins.If you are asking, "What is the relationship of your uncle's son's daughter to you?" she is your first cousin once removed.
Your cousin in law
If her son is from a previous relationship, then he would be your step-son.
I believe they would be great aunts or great uncles.
Your grandmother's sister is your great aunt, her grand children are your second cousins twice removed. Genetically speaking this is barely a relationship - but if you were raised together as cousins the familiar bond can be tight.