Your nephew's son isyour great nephew. You are his great aunt or great uncle.
Yes, there have been several popes that were related - one father and son and several popes had nephews who were elected as pope.
The sons of your son-in-law's siblings are his nephews. You are not related to them.However, your son-in-law is married to your daughter. The sons of her siblings are also your son-in-law's nephews. They are your grandsons.
your nephews
Great nephew
3rd cousin
Fili and Kili are his nephews.
they are cousins
Yes, they are his nephews.
They are your nieces and nephews.
If your great uncle married into your family some of his nieces and nephews are your aunts or uncles (or your parent) and some are not related to you at all.
Your father's great nephew is the son of your father's niece or nephew. Your father's nieces and nephews are your first cousins. Their children are your father's great nieces and great nephews, and are your first cousins, once removed.
You would be his Great Uncle and he would be your Great Nephew.