Pinchas Was The Grandson Of Yisro?

This parsha-related dilemma has been bothering me for years. Rashi, citing Sotah 43A, writes in one of his first comments on last week's parsha that Pinchas was a grandson of Putiel, otherwise known as Yisro, the kohen Midian and father-in-law of Moshe Rabbeinu.

The Tribes scorned him: "Have you seen this one, whose mother's father [Jethro] fattened calves for idolatry!

As someone who is a stickler for stuff like continuity (lehavdil: woe be unto those who retcon older, established comics/books/movies/whatever for newer material), I have tried to figure out how this works out timeline-wise with Pinchas' age and yetzias Mitzraim.

We know that Pinchas wasn't annointed as a kohen like his father, uncles, and grandfather, because he was an already living grandson of Aharon, as we see in Shemos 6:25, which first introduces Pinchas and his lineage while Bnei Yisrael are still in Mitzraim:

25 And Eleazar Aaron's son took him one of the daughters of Putiel to wife; and she bore him Phinehas. These are the heads of the fathers' houses of the Levites according to their families.

I'm pretty sure the switcharoo which exchanged the first born sons (who were meant to be the kohanim) with Aharon's family occurred shortly after the Chet Ha'Egel. This incident with Bilam and Balak took place much further along, right before Bnei Yisrael were to enter Eretz Canaan.

So that rules out the possibility that Elazar married one of Yisro's daughters who he might have brought with him (along with Tzipora, Gershom and Eliezer) when he arrives at Bnei Yisrael's camp in the Sinai Desert. There is also no textual evidence of him bringing any other family with him.

When Aharon and his sons were annointed kohanim, by extension, future as-of-yet-unborn descendents would also become kohanim. Bummer for Pinchas who was already alive and thus missed out.

However, thanks to his heroic act of spearing Zimri and Cozbi, HaShem grants him the bris shalom, as well as kehunah.

Yisro, when we meet him in the Torah, lives in Midian, where Moshe marries Yisro's daughter, Tzipora, when he ends up spending time there after fleeing Mitzraim.

There is another possibility as to when and where this marriage took place - in Egypt itself.

Per Sanhendrin 106 A, Yisro, Iyov, and Bilam were advisers to Pharaoh at the time he was trying to figure out what to do about the "Jewish problem." Bilam said to throw the baby boys into the Nile, Iyov said nothing, and Yisro ran away.

Hence, it stands to reason that Yisro left some family behind in Egypt - though I have no idea who else besides this daughter that Elazar marries would have remained after he fled from Pharaoh - perhaps his original wife...?

Thus, it would seem that the most logical thing is that Elazar married a daughter of Yisro from his that time spent time in Egypt as one of Pharaoh's advisors.

This would make Elazar's wife a bit older than him. I'm not going to go into age differences here, but we know of several famous Tanach couples where the woman was much older than the man... like Moshe's own parents.

Incidentally, it's neat that both Moshe and his father-in-law fled from Pharaoh's wrath and ended up in Midian.

In conclusion, I think Elazar married a daughter of Yisro who was born in Egypt and left behind after her father fled Egypt.