Well, the French usage for names generally is just to use either a straight French pronunciation based on how the name is written, or an approximation of the foreign pronunciation using sounds that exist in French. Only a handful of well-known names get to have a special pronunciation.
If your family has been in France for 100 years, I wouldn't say they pronounce the name "incorrectly", they just pronounce it the correct way in France.
It was common knowledge nearby that anyone who came in and pronounced it "ver-sai" was from out of town. Because everyone living there called it "ver-sails".
I use this as an example of how if anyone gets to decide how something is pronounced, it's the people who live there. The city is simply called "ver-sails" and that's all there is to it.
It is not "wrong", anymore than pronouncing it as you likely say "karate" is not more wrong than "ka-ra-te" (the japanese pronunciation) or that the japanese prounciation of the english word "sweater" being "su-we-ta" is wrong. Borrowed word pronunciation is entirely up to the user.
I also love the double mind-fuck of "karaoke":
EN: pronounced "owe-kee"
JP: "oh-keh"!
EN: but "oke" comes from the English "orchestra" (kara-oke = empty orchestra)… so really should be pronounced "or-keh"? Are we mispronouncing a Japanese mispronounciation of OUR OWN WORD??
(and then of course the Greeks chime in, OG)
Detroit would be the same way if it wasn't such a big city. Easier to see when you add back the accent, Détroit.