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 brother's daughter's daughter is your great niece.
great uncle
His great uncle
The grandchildren of any of your great uncles and great aunts are your second cousins.
Your daughter's son is your other daughter's nephew and she is his aunt.
your uncles daughter would be your cousin
Your uncle/aunt's son/daughter is an adult and you are still small, your uncle/aunt's daughter had a child, and that child will call you uncle. Uncles/aunts are your dad/mom's siblings.
Your uncles daughter would be your cousin.
your uncles daughter would be your cousin
Your daughter's son is your grandson and you are his grandparent.
2nd cousin.
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.