Are your great niece and your son related?

Answer 1

Yes, of course your son and your great niece are related. They are first cousins, once removed, to each other. (Your great niece's parent, your niece or nephew, and your son are first cousins to each other.)

Answer 2

Your son and your sister's child are first cousins.

Your son and your sister's grandchild are first cousins, once removed.

Your grandchild and your sister's granschild are second cousins.

Answer 3

Your son and your niece are first cousins. Your son and your niece's son are first cousins, once removed.

Answer 4

No. Your son's wife is your daughter-in-law, but her niece has no common ancestor with you and so is not related to you.

Answer 5

The parent of the great niece and your son would be first cousins. There is a difference on one generation between the two. That would make them first cousins once removed.