Here's how I look at this:
Tolkien's latest word on the matter appears to be
Gil-galad son of
Arothir (
Orodreth), with Arothir being the son of
Angrod.
Unless I missed something (possible of course), I don't think this contradicts anything Tolkien himself published, at least.
Here's my longer answer, though you might have read this elsewhere, if you are elsewhere
Elainiwen. And I think double posts at this site are auto-merged? Anyway.
For myself, here I won't hold Tolkien to never published (by him) texts to (try to) work out how his last known idea might be implemented.
Gil-galad barely appears in QS, and
"but his young son Ereinion (who was after named Gil-galad) he sent to the Havens" could be noted of Orodreth rather than
Fingon, for Orodreth is noted as the warden of Tol Sirion before being forced to flee to
Nargothrond.
Other manipulations regarding Orodreth's place in the family tree seem slight enough: alter
brother to
nephew where
Finrod or other brothers are involved, and from
Of The Flight Of The Noldor:
"and Orodreth, alone of his sons spoke in like manner" -- one could alter
sons to
kin, or house perhaps, or simply delete this reference (as he would now be Angrod's son).
And stripping
Finduilas of her line to
Turin (or altering it) does not seem that invasive in my opinion, which line does not occur in QS itself if I recall correctly [referring to:
"But you are kingly," said she, "even as the lords of the people of Fingolfin; I would I had a brother so valiant." The Children of Hurin].
For examples. That said, the Nargothrond matter is "the thing", in my opinion. Starting with Gil-galad as
Felagund's son, the external progression seems to be:
A) Felagund sends his wife and son to the Havens for safety, or A1) demands that Orodreth do so, or A2) Felagund's wife forsakes Nargothrond with Gil-galad
B) Then later the idea re-emerges that Gil-galad was sent to the havens, by his father Fingon.
C) Then later again Gil-galad is back as a Finarfinian, but now "escapes", I assume escapes the fall of Nargothrond.
The later idea might raise the question of why Finduilas -- she becoming the sister of Gil-galad -- did not journey with him to the Havens; or, if A2 were to be the case, why a wife and child forsaking Nargothrond would not include the female child Finduilas.
But again, if Gil-galad is present at the Fall of Nargothrond, Tolkien would arguably provide a way in which he escaped, but Finduilas did not.
Another matter might be: if Gil-galad is Arothir/Orodreth's son and not merely a child when Turin shows up, how does Turin grow so high in Orodreth's councils? Orodreth is weak and simply favors Turin? Possible, but on the other hand this is...
...
Gil-galad!
Anyway, the simplest solution
so far, it seems to me, is to have the Finarfinian Gil-galad be somewhere else during Turin's rise in Nargothrond, and its fall.
