In the books, Niall is Sookie's great-grandfather. Niall has a half-fae son called Fintan, who has a son called Corbett. Also in the books Claude&Co are Niall's grandchildren but this is not true in the books. The rest of this post will deal with what the show says. ANYWAY...
A lot of articles and even the Wikia once incorrectly stated Niall is Sookie's great-grandfather. What Niall actually said was "I'm your fucking fairy grandfather". I think an important distinction is to be made between normal grandfathers (e.g. Earl) and a fairy grandfather (Niall).
Let's look at the Stackhouses:
- Niall said his son John William Stackhouse signed the Warlow contract in 1702.
- Jonas Stackhouse, born in 1801, moved to and built the Stackhouse home in 1834. He died in the 1870s.
- Earl Stackhouse died in 2009. He was probably born around 1930s.
Assuming human lifespans, this suggests: Niall > John William > X > Jonas > X > Earl > Corbett > Sookie/Jason. It is possible John William was a hybrid like Sookie and maybe showed extended lifespan, so his son could be Jonas. I don't think we know about human-fae hybrid lifespans yet. I am also assuming Sookie is a direct descendant of John William as the contract, if I remember correctly, specified a Stackhouse. If Niall has other sons, I don't think they all would have taken the Stackhouse name as Niall's last name is Brigant.
In this bloodline, were any of the sons hybrids?:
- Earl showed telepathy but we did not see any light powers. However, Earl was admitted into Queen Mab's realm which harvested hybrids, but Jason was not. This suggests Earl actually has the activated fae gene but probably hasn't had any help activating his light powers. Telepathy seems basic as Sookie could do it as a child. So Earl is a hybrid.
- No idea about Jonas or John William. John William was described by the Faerie Elder as "handsome", similar to how Jason is handsome thanks to his Fae blood but he has no light powers. However, I think everyone with fae blood is suppose to be attractive, so really we have no idea about John William or Jonas. I would have thought John William is not a hybrid because he no longer used the Brigant name and signed the Warlow contract. All hybrids have faerie godparents (e.g. Claudine to Sookie) so it might be that John William was simply in the loop about fae (like Jason is). However it is, of course, possible that John William simply did not want to die but was a hybrid. No idea about these two!
So why is Niall called a fairy grandfather?:
- Perhaps Sookie's fairy father is Earl, who showed fairy powers too. The next one in the bloodline could be Niall (if Jonas and John do not show fae powers), which would make Niall her faery grandfather.
- If John William was a hybrid, then Niall would be Sookie's fairy great grandfather.
- Or the shows just doesn't bother calling Niall her great-great-great-great-great grandfather, and just keeps one "great". It's just titles and this isn't paid much attention to in the show.
Is Sookie half-fae or what?:
- Interestingly, in a Season 5 episode ("In the Beginning"), Claude&Co tell Sookie she is half-fae so her powers are finite. However, in S6E2 Niall says "part fae" and it is clear Sookie cannot be half-fae.
- Following the bloodline and assuming one parent is fully human AND assuming human-like lifespans, we have:
- Niall 100%
- John William 50%
- X 25%
- Jonas 12.5%
- X 6.25%
- Earl 3.125%
- Corbett 1.5625%
- Sookie 0.78125%
- So it seems Sookie is between 0.78125% and 1.5625% fae (if the first X is present or not present). If the fae gene acts differently (due to magic!), this might be different. For example, it might remain the same if the child is like Jason who doesn't show powers.
- If lifespans are not human, then we can cut out the two Xs. Sookie would be 3.125% fae. Not that much better!
I really wish this show would make relationships a bit clearer as they are deviating from the books. Perhaps they are not making things clear as it allows them to randomly throw in new characters (e.g. "some Stackhouse signed a contract!" = new storyline).