What is the relationship of your uncles son daughter to you?

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.