What relation would your grandson be to your nephew?

Answer 1

One opinion:

second cousin

Another opinion:

They would be first cousins once removed.

Explanation:

You first need to find a common ancestor. That would be your father. Now count down from the common ancestor. People on generation 1 would be siblings (you and your brothers and sisters). People on generation 2 would be first cousins. People on generation 3 would be second cousins, and so on.

In this case, the people in question are in different generations. So you count down until you find the first person in question, which would be your nephew. Your nephew and your son are first cousins. For each generation further you have to count down to find the second person, you add a "removed." So your grandson is your nephew's first cousin once removed. To carry this on, your great-grandson would be your nephew's first cousin twice removed.

It's easier to understand if you draw this out on paper.