Your great uncle's daughter would be your aunt.
The grandchildren of any of your great uncles and great aunts are your second cousins.
Your aunt is your child's Great Aunt, so your child is her great niece or great nephew.
great uncle
Your brother's daughter's daughter is your great niece.
your uncles daughter would be your cousin
Second cousin, twice removed
I believe they would be great aunts or great uncles.
your uncles daughter would be your cousin
Your uncles daughter would be your cousin.
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.
His great uncle
Your daughter's uncle can be your brother. Her parent who is not your sibling (your brother-in-law or sister-in-law) could also have brothers. They will also be your daughter's uncles, but will not be related to you.